Building wpmu with developer / cutomer profiles... HowTo

Im building a WPMU where developers will be able to create an account and build sites on the network for there customers. I would like to create as little plugin writing as possibly, and if someone could point me in the right direction on how to achieve this, i would have you in my prayers tonight

Developers will have there own profile, with there previously created work for other customers.

The customer can browse the developers near them, and see there profile. They can then ask them for a quote on there job.

Much like freelancer.com or one of the 100 other sites with it-workers.

I know this cant be done only with plugins, but if someone could point me in the right direction on some parts of the project, i would be very happy...

All i have figured out now, is that Pro site + can take care of the sites, and after the developer has finished the site, the customer can be set as admin for the site, and he can upgrade to payed hosting to get his own domain, and from there take over the site...