Working at startups is always a gamble. But if you get your foot in the door early enough at the right company, you could end up a millionaire.

Inspired by a 2012 Quora thread, we came up with our own list of companies you should join if you want to make some serious cash in four years, assuming you're able to negotiate a bunch of stock options when you join.

We've included employee count for each company. For startups whose employee headcounts we didn't have access to from our own reporting, we consulted Pitchbook, a private equity and venture capital database that tracks information about companies.

The companies on this list are blowing up — some are early-stage, some are more mature — but they're all highly valued and fast-growing. You'll want to get hired before they take off further.

 

Thumbtack

 

Headquarters: San Francisco

Investment raised to date: $273.2 million

Employee count: 366

Founded: 2008

Thumbtack, one of the newest entrants to tech's still-booming "unicorn club," is a platform that matches professionals like personal trainers or electricians with potential customers.

Earlier this year, Thumbtack raised $125 million at a $1.3 billion valuation. That's quite a spike from the company's $750 million valuation last year. Thumbtack handles job listings and marketing for people providing local services, and collects interested customers.

 

Lyft

 

 

Headquarters: San Francisco

Investment raised to date: $1.01 billion

Employee count: 500

Founded: 2012

Though it's often compared as a smaller rival to Uber, Lyft is a huge entity in the on-demand ride-hailing market. With a $2 billion valuation, Lyft operates in about 65 US cities, and recently announced a huge partnership with Didi Kuaidi, the highly valued Uber rival, to expand its footprint overseas.

Lyft's investors include Rakuten, Alibaba, and even Carl Icahn. This year alone, Lyft raised two major rounds of funding — $530 million in March and another $150 million from Carl Icahn in May — rebranded with a more sophisticated look, and announced huge growth for the company.

 

Zenefits

Parker Conrad and Laks Srini.

Headquarters: San Francisco

Investment raised to date: $583.6 million

Employee count: 1,445

Founded: 2013

Zenefits, a startup aimed at making administrative tasks such as payroll and benefits easier, is shaping up to be one of the fastest-growing cloud companies ever, in revenue and number of users.

In May, Zenefits raised $500 million in Series C funding, bringing the company’s valuation up to $4.5 billion. Only two years old, Zenefits employs 1,000 people and has 10,000 customers.

 

Harry's

 

Harry's

 

Jeff Raider and Andy Katz-Mayfield.

Headquarters: New York

Investment raised to date: $287.1 million

Employee count: 535

Founded: 2011

In less than two years, Harry’s cofounders Jeff Raider and Andy Katz-Mayfield launched their online shaving service, raised more than $200 million in funding, and purchased German razor factory Feintechnik, where their products are produced, vertically integrating the company. Harry’s raised $75 million in venture funding in November 2014 and another $75.6 million in a Series C round in July, not to mention the $122.5 million they received back in January 2014. As of this summer, the startup was valued at $750 million post-money.

Raider and Katz-Mayfield first came up with the idea after a trip to the drugstore where Katz-Mayfield found himself overpaying for a poorly branded product and frustrated by the lack of customer service. They knew there had to be a more efficient way to purchase razors — and Harry’s was born.

 

Slack

 

Headquarters: San Francisco

Investment raised to date: $339.95 million

Employee count: 142

Founded: 2013

Slack is an insanely popular workplace communication app. Slack has a group chat room, private chat features, and lets users share files and work collaboratively too. Slack was originally an internal tool used by CEO Stewart Butterfield's team at Tiny Speck, the company that made the multiplayer game Glitch, but Butterfield decided to spin it out into its own product and company. 

Earlier this year, Slack raised a $160 million round of funding at a $2.8 billion valuation. Slack's growth as an enterprise communication tool has been completely organic — Slack hasn't spent any money on marketing. It's one of the fastest growing enterprise apps of all time.

 

Giphy

 

gipfy

Headquarters: New York

Investment raised to date: $23.95 million

Employee count: 16

Founded: 2013

Looking for the perfect GIF? Let Giphy do the work for you. Type in any keyword or phrase, such as “happy puppy,” and the search engine generates hundreds of related GIFs for you, making it easy to add that cute puppy to a text or email.

But the startup is more than an addictive way to send GIFs to your colleagues: In January, itraised $17 million in a series B round of financing led by Lightspeed Venture Partners, with participation from General Catalyst, Lerer-Hippeau, RRE Ventures, CAA Ventures, and Betaworks, bringing its post-money valuation up to $80 million. Not bad for a company that’s less than two years old.

 

Oscar

Oscar

 

Oscar CEO and cofounder Mario Schlosser, cofounders Kevin Nazemi and Joshua Kushner.

Headquarters: New York

Investment raised to date: $327.5 million

Employee count: 223

Founded: 2013

In April, health-insurance company Oscar raised $145 million, giving it a $1.5 billion valuation. In September, Oscar closed another $32.5 million round of venture funding led by Google Capital, pushing its valuation up to $1.75 billion. 

Oscar wants to transform the healthcare industry by creating a better user experience when it comes to health insurance. It launched publicly in 2013 and had more than 40,000 customers across New York and New Jersey as of April, with plans to launch in Texas and California.

 

Pinterest

 

Pinterest

 

Headquarters: San Francisco

Investment raised to date: $1.32 billion

Employee count: 731

Founded: 2009

Pinterest, an online scrap-booking site that lets users organize photo pins onto different boards, is now valued at $11 billion after raising a $367 million round of funding in March, followed by another $186 million in May. Investors include Andreessen Horowitz, Fidelity Investments, and Bessemer Venture Partners. 

The site continues to grow and adapt its business model, most recently releasing new options for advertisers. Instead of just choosing to pay for views or clicks on promoted pins, advertisers can choose to pay with a cost-per-engagement model or cost-per-action model.

 

ClassPass

 

ClassPass

 

Headquarters: New York

Investment raised to date: Undisclosed, though Crunchbase lists total funding at $54 million

Employee count: 180+

Founded: 2013

Gym rats love ClassPass, a service that lets users take unlimited classes (up to three per location) at boutique fitness studios for a monthly flat fee. Not only does ClassPass give users a steep discount on pricey classes like Pure Barre and FlyWheel, but it allows them to try a multitude of things, from spin to hot yoga to Pilates.

Investors are pretty keen on ClassPass as well. The startup is valued at about $400 million, and raised $40 million in January in a series B round of funding led by General Catalyst Partners and Thrive Capital, bringing its total amount of venture capital raised to $54 million since its launch in 2013.

 

Blue Apron

Headquarters: New York

Investment raised to date: $193 million

Employee count: 2,500

Founded: 2012

Blue Apron, a company that makes cooking easy by delivering perfectly proportioned ingredients and recipes straight to your door, isn’t just a godsend for lazy cooks — it’s also super valuable. Following a series D round of funding to the tune of $135 million in June, the startup announced its $2 billion valuation.

Though it’s only been around since 2012, Blue Apron is already selling more than 5 million meals per month. CEO Matthew Salzberg says the company makes money on every meal and that its retention rates are "really, really strong." 

The startup has more than tripled in size since January, and reports hundreds of thousands of customers. Blue Apron’s potential is vast: The service appeals to millennials who want to expand their repertoire in the kitchen as much as busy moms straining for creativity and simplicity in their weeknight meals.

 

Snapchat

Snapchat

Evan Spiegel of Snapchat attends TechCrunch Disrupt SF 2013 in San Francisco.

Headquarters: Venice Beach, California

Investment raised to date: $1.19 billion

Employee count: ~100

Founded: 2011

Spiegel dropped out of Stanford University just a couple credits shy of a degree to create Snapchat, the ephemeral multimedia mobile messaging app. Snapchat is on track to generate$100 million in revenue this year.

Snapchat has received $1.19 million in funding and has a $16 billion valuation — higher than almost any other US-based private tech company.

 

Sprinklr

 

Sprinklr

Headquarters: New York

Investment raised to date: $123.5 million

Employee count: 1000+

Founded: 2009

Earlier this year, Sprinklr, a social-media management firm that competes with companies like Hootsuite, raised a $46 million round at a $1.1 billion valuation. 

Sprinklr nearly doubled its valuation in a year. When the company closed its last round of funding, a $40 million Series D round in April 2014, its valuation was $520 million. In August, the startup also acquired TBG Digital, one of Facebook’s big ad-buying clients.

 

Okta

Okta

 

Headquarters: San Francisco

Investment raised to date: $230 million

Employee count: 600

Founded: 2009

Todd McKinnon is a former star Salesforce engineer who launched his own company in 2009 without CEO and friend Benioff's blessing. His cloud-security company, Okta, has seen massive growth: By September 2014 it had raised $155 million from top VCs, and has now received $230 million. Okta is now valued at about $1.1 billion and is expected to go public by 2016.

McKinnon said there's tremendous value in working for a rapidly growing, successful company before pursuing other endeavors. He called his time at Salesforce a "gift" that taught him what it means to win.

 

Compass

Compass

Headquarters: New York

Investment raised to date: $123 million

Employee count: 207

Founded: 2012

Launched in 2013, Compass (formerly Urban Compass), helps people find neighborhoods and places to live — either renting or buying. It has attracted over 350 agents to the company already, with more of half of them in New York.

Compass has already shaken up the real-estate industry in New York and DC. It recently raised another $50 million to expand all over the US. The funding, led by Institutional Venture Partners (IVP), brings total funding to $123 million and values the company at $800 million, according to a source familiar with the matter.

 

Bond Street

 

Bond Street

 

David Haber and Peyton Sherwood.

Headquarters: New York

Investment raised to date: $112.2 million

Employee count: 11

Founded: 2013

David Haber and Peyton Sherwood are coming after Wall Street banks with their startup, Bond Street, and Wall Street has begun to take notice. Bond Street is eating into the business of some major banks by making loans to small businesses.

This summer, Bond Street pocketed a whopping $110 million investment from Jefferies investment bank and Spark Capital, where Haber previously worked. Some investors, like Airbnb cofounder Nathan Blecharczyk, also participated in the round. The new funding will be put toward expanding Bond Street from eight to 25 full-time people next year. "We'll probably expand that even more to 40 within the next two years, but we'll see," Haber told Business Insider.

 

YouNow

YouNow

 

Headquarters: New York

Investment raised to date: $41 million

Employee count: 40

Founded: 2011

Teens are obsessed with live-streaming mobile app YouNow. The interaction between performers and their audiences is what sets YouNow apart from other buzzy live-streaming services such as Periscope or Meerkat. The average mobile session on YouNow is about six minutes. The average mobile broadcast is about 18 minutes.

Founder Adi Sideman says 70% of YouNow's users are under age 24 and that the platform has 100 million user sessions a month, with about 150,000 broadcasts daily. For comparison, Twitter announced earlier this year that its live-streaming app Periscope hit 1 million users in its first 10 days.

 

Stripe

 

Stripe

Headquarters: San Francisco

Investment raised to date: $280 million

Employee count: 247

Founded: 2010

Last fall, Apple announced partnerships with a number of retailers and payments companies for its Apple Pay service. Among them was Stripe, a five-year-old mobile-payments startup.

In July, Stripe raised a $90 million round of funding from American Express, Kleiner Perkins, Sequoia Capital, and Visa. The round of funding valued Stripe at $5 billion.

 

Vox Media

 

Vox Media

 

Headquarters: New York

Investment raised to date: $307.6 million

Employee count: 328

Founded: 2003

Vox Media, the media company that owns The Verge, Curbed, SB Nation, Vox.com, and Eater, added another site to its arsenal in June: 18-month-old Re/code, a tech-news publication founded by Walt Mossberg and Kara Swisher in 2014, which is predicted to bring in $12 millionthis year, Business Insider reported at the time of the acquisition.

In addition to purchasing Re/code, Vox Media received a $200 million investment from NBCUniversal in August. The investment is reportedly part of a push by NBC to connect with Millennial audiences, Re/code reported at the time, but it’s a good sign for Vox Media any way you slice it. With this investment, Vox Media is now worth $1 billion, according to The Wall Street Journal.

 

DraftKings

 

 

Headquarters: Boston

Investment raised to date: $375 million

Employee count: 222

Founded: 2011

DraftKings is a $1.2 billion daily fantasy-sports site that lets its users bet real money on their teams. You may have seen its ubiquitous TV advertisements telling you about how some of its members have cashed out crazy sums of money using DraftKings.

The startup is also mired in controversy: Earlier this month, the New York Times reported that a DraftKings employee admitted to "inadvertently releasing data before the start of the third week of N.F.L. games." That same week, the employee won $350,000 at FanDuel, DraftKings' biggest competitor in the daily fantasy sports business.

DraftKings, Boston-based startup, has raised $375 million in venture-capital funding from investors like MLB's venture arm, Melo7 Tech partners, the NHL, and Redpoint Ventures.

 

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