If you add her to the lease, make sure it is specific as to whether if he leaves, she does too and that the deposit you got is from him.

You are right that you deducted damage from the security deposit and so he is entitled to less than the full deposit back.

Fifth, elements outside your planning or control can increase expenses significantly; tax increases due to budgetary shortfalls, insurance costs doubling due to natural disasters, tenant damage beyond what the security deposit will cover.  

If they caused it well the damage deposit could be in play too.

If it's a very new lease, you'd provide copies of the security deposit and first month's rent with proof of deposit.   

When they see a large deposit, they will want that explained with a paper trail.

The issue I find is that when I go to list my units, which are clean and moderately upgraded apartments in Little Havana and Allapattah I literally have 70 applicants in 24hrs via facebook marketplace or through the apartment rental platform my property management software interfaces with (like Apartments.com etc).So when I have 70 people lining up with first, last and deposit with no other middleman or agency impeding the process or requiring inspections or causing delays or requesting additional paperwork be filled out where is my incentive to go the section 8 route?

Typically, they ask for an earnest deposit of $2500 or so on your CC.

And one must ask themselves WHY anyone 'advertising' to teach others, won't agree to "share the risk" by meeting someone 'half way' for say a minimal down payment, then "doing the work" necessary, or they LOOSE their' deposit?!'

This was included in the initial contract we signed when we put the $1,500 deposit.