Is Multisite really capable of Etsy-type setup

I'm having a real problem - I purchased Multisite explicitly to create an Etsy style marketplace site. Now after a great deal of work I've realized I need a developer's help to actually set this up - the plugins and themes I've received are creating all kinds of issues.
Now I have arrived at the point where a developer - who I have found through your job submit area and who seems good - is giving me a statement of work to approve. It begins this way:
Scope : Marketplace for Celtic jewelry where admin will take a percentage of the sale. It will offer vendors an option to set up a store as with Etsy, and I will take a percentage of the sale. Store owners are responsible for shipping, returns, etc.

Problem : There is no ready made plug in available , So need to implement with the combinations of plugin.

What's going on here? The first part describes an ETSY like implementation in clear terms, but the developer is telling me that your plugins and themes cannot do this. I'm really having a hard time understanding what I purchased. Please clarify.