I would require a signed lease from them as well as a security deposit. 

Need proof of insurance, deposit etc. etc.

So just recognize this could be lengthy process if they default.If it was me, I would take it as a non-refundable deposit with a letter of intent and a purchase and sale agreement that the money is a down payment, is not refundable and they must execute the closing by a specific date otherwise they forfeit the money.

Theoretically, I could advertise "no deposit" and charge something like a $500 move in fee, which is non refundable.

@James WiseHey, I just want to say I was told in another forum post I am mean and it was irresponsible for telling a potential homebuyer who did not have earnest money deposit that if you don’t have the money for earnest money deposit that should not be buying a houseBecause a 23 year old living with mommy and daddy’s mansion says they buy all the time with no money down….So why you trying to kill their dreams - Lightbulb moment!!!

Someone I know owns section 8 properties, he doesn’t have any issues and the rent gets deposited directly to his account.

That consideration usually in the majority of contracts is an Earnest Money Deposit (EMD). 

Additional prior to move-in deposits: Cleaning Deposit $400.

If you are set on self managing though, here are answers to your questions:- Most of the time in the U.S. it is just first month's rent and security deposit, I believe that this is actually determined by laws that vary from state to state.

Glad to hear that most of the people here are also concerned.I haven't been asked for any fees or wires yet, just the application (which I haven't filled out). there is no 6 to 7% interest loans  the only exception is a local community bank where you would have substantial deposit relationship a local project etc..