For thoughts on this, see this thread:

http://www.retouchpro.com/forums/critiques/17378-painted-portrait-hobby-money-maker.html

Definitely check out the Karen Sperling article (.pdf format) in post #7.

If the link to Karin's .pdf breaks someday, which it probably will, send me an e-mail [click my name above], (not a Private Message) and I'll send it to you.