For a marketplace, you have an advantage doing it this way. Initially, there wouldn't be a lot of users. So badly performing code wouldn't necessarily matter so much. If you happen to have a Twitter style growth, FailWhale is a good kind of problem to have.

Look for some of the PHP marketplace scripts. Actually, Dating is a typical marketplace (for people). If you have design skills, you can replace the graphics and text and you should have a semblance of a starter site rather quickly.

Whatever you do, only offer equity on the basis of people delivering working code. Otherwise, you'd have a ton of free lodgers.