I've yet to find out how to run retail photography effectively....
Not sure if it is actually possible to make money with a pure retail photography store where that is all you would do. I played around with photography this morning for a few hours and the Tend Photo Studio mechanic is similar to playing for tips on an instrument. If there are nearby Sims, then the game will periodically have a Sim walk in front of the camera, pose, and toss you a mere $10 per shot. You might get 2-3 shots in the couple of hours for an entire Tend Photo Studio queue. The photos themselves that are then tossed into inventory could be sold in the store, but even at a exorbitant price markup you're looking at less than $100 per photo compared to Masterpieces that can go for $10k +.
What seemed to make more sense to me would be to set up a combined fine arts studio where selling paintings is where the real money is and you could have a photo studio inside as well as something to do now and then. But, it would fit the theme nicely of that kind of retail shop.