It sounds like PSM is software image management tool, and I am looking for something to just handle basic Photography Studio Management functions can you use it to just manage sales, inventory tracking, finance and customer information?

Absolutely, image management and fine art sales tracking was just added to support those Photography Studios like our own  that have this requirement.  All of the forms, work-flow and tools work the same without using the image management functions you would not notice any difference, invoices for instance can be printed with or without images.