Some initial questions for someone from Ning thinking of mocing over
Installation and Configuration
http://paul.jamroomnetwork.com/jamroom5-2b/
Its one of my old test sites. Not much on it expect a couple of test blogs but it'll give you an idea.
You could specify two quotas, professional and amateur, then if artists were placed in the appropriate one, the professional quota could be specified as a search parameter when generating lists.
Alternatively, you could create a member option for them to select if they are pro or am, then do a similar search based on the option.
hth
updated by @paul: 12/29/14 09:23:54AM