Absolutely not. Small or part-time creators are strongly encouraged. Blue Mars will not be too different from
SL. In
SL, to sell content on a small scale you might rent a small space, have a seller add your stuff to one of his/her vendors and you give them 10%, etc.
In Blue Mars there will be City Owners (equivalent to the Estate or Region owners in
SL). The city can then be parcelled and rented out in much the same way as people rent parcels in
SL.
The main difference is that content is exclusively created outside of Blue Mars, then uploaded. However, apart from creating prims, a great deal of creation is done outside of
SL too, eg textures, sounds, video, animations, then uploaded for a fee,
In Blue Mars however (and this is the real difference, and this is only from what I gather, so don't take it as gospel), only city owners or their tenants can upload content. So you would have to either rent, or get a vendor owner to upload it for you into his vendor. But this does really need to be confirmed in the beta tests.
I will add your question to a growing list I have now for a follow-up interview with JS.
Rock