how much $$ do you want to make / hour ?
you can always do it that way ...

or ..
sitting fee + cost of film and materials up front.
price for finished prints back end.

go to a pro-lab and find out how much they charge
for the sizes you want to sell, and then triple them ( or at least double them ),
and come up with some sort of package deal, like they do at
kiddie candids or jc penny or ... ( fill in the blank ) for 'sheets" ..

i wouldn't waste your polaroids on portrait proofs, polaroid film is too expensive + rare these days
to do that with it

good luck!