Currently Senior Product Manager for APIs and Platform features. Formerly lead platform-related Business Development at New Relic. San Francisco native. Expertise in Biz Dev, Platforms, Integrations, API Ecosystems, Partnership Agreements, Startup Partnering, etc.
I've heard great things about https://www.upcounsel.com - I haven't used them personally, but they went through the same startup incubator that I did (AngelPad in SF) and the other AngelPad firms that use them have recommended them highly.
Focus on the more difficult side of the marketplace.
For instance, if you think it'll be easier to get suppliers, then focus first on getting buyers - always be working on your toughest problem (aka your biggest risk).
You'll find some great blogging on Marketplace and Platform topics here http://platformed.info (read the ebook too!)
Go to work at an mid-stage, venture-backed startup where:
* You get lots of options ("lots" being relative to the stage of the company and the % of ownership you'd get at other companies of a similar stage and risk - "lots" can be difficult to determine ; )
* The business is executing well
* Much of the risk has been removed, but this isn't well-understood by the market in general (this is part of why you'll get "lots" of options rather than "very few" options)
* The company is running roughly at break-even, or could be if it dialed-back hiring/marketing a bit
* The company is within a few years of going public
Then, work like crazy, make the place a huge success, and ask for additional options as often as you reasonably can.
Ideally you'll end up with enough options that you'll have $1M soon after IPO.