I presume you still hold a security deposit so you could still punish them if you'd like but what if you didn't and left on good terms?

I just want to see what each person paid, (rents all the same in each house, though I they have given me different amounts in the 2 months they have been there), what they should have paid (students), what they owe, what their security deposit was. 

Do you have it in your lease that accumulated late fees can be taken out of the security deposit? 

require a sizable deposit.

My wife spends about 15 to 20 hours a week taking payments, paying bills, making deposits, and doing the accounting. 

You'd need to know what kind of lease, how far behind, is there a security deposit, what claims the is tenant making, if any.  

Decided to switch property manager at the end of March, and asked for the final payment from ABC with all the security deposits that they were holding from my tenants  and some  miscellaneous fees that were paid, also including February rental income that was never deposited into my bank account.

I get the calls every week when the buyers is about to lose their deposit and in need of being saved.

Seller - wholesaler and wholesaler - cash buyer.Cash buyer deposits the funds in the second escrow. 

Tell your cash buyer you need a minimum $2k non-refundable deposit made out to you or your company at the time you assign your contract to them.