Investment Property Purchase - How to handle security deposit?

[Chase Gibson]

I am closing on my first investment property soon and was hoping to get some insight regarding the following question.  I am fully aware that I will be getting the deposit from the current landlord at closing.

If you purchase a property that has tenants in it, how do you go about determining their refund of the deposit when they move out?  How can you prove/justify that any required repairs that the deposit will be used to complete are truly from the tenants and were not already present when they moved in?(Current landlord does not have pictures or a move in inspection report)