More brainstorming:
The cheapest and fastest way to get it off the ground might be to use a hybrid approach: a central website built in something like
Drupal, with each individual service sold through online store platforms. Each member-seller could sign up for their e-commerce platform separately. There might be complex store requirements (products vs. services, physical delivery vs. virtual delivery), so each vendor may want different features.
If you try to build an entire e-commerce platform from scratch, it's probably going to cost tens of thousands of dollars, as well as being very time-consuming with managing orders, customer service, and sellers who aren't administering their sections well. It might get so complicated that it requires multiple full-time employees.
If you use only the external e-commerce store platforms, they may not have good features for managing multiple sellers, and dealing with order fulfillment from multiple sources.
Combining the two would take the burden off of the central website for customer service and fulfilling orders, and would reduce the workload for member management. If a few members are not fulfilling their orders well, it wouldn't reflect on the central website as much as on the individual vendors. The central website could function more as a showcase and marketing platform than the actual transaction platform.
With a hybrid approach like that, the costs could be very low:
- Drupal: free. It already has built in features for user registration, permission levels, product showcase, etc. Whatever features it doesn't have, can be added on with PHP/HTML/CSS. It might only take a week or two to build a website like this.
- E-commerce software: independently obtained by each seller. Some of the services work on a commission only basis, so there are no upfront costs. Each member's showcase could link to their external store.
- Hosting: USD $60/year.
- Domain name: $15/year.
- Labor: management of sellers -- this would be reduced by using external e-commerce software
- Labor: customer service -- this would be reduced by using external e-commerce software
- Labor: web development -- negligible, if it's done on volunteer basis
- Labor: maintenance -- negligible, if it's done on volunteer basis
- Legal: probably not more than a couple of thousand USD.
With this kind of setup, it could be launched with less than USD $100, not including any legal fees.
The crowdfunding campaign could be used to raise a little bit of cash and get publicity. I think that IndieGogo has flexible funding, so you can still get paid if you don't reach the goal.
Just brainstorming...