3.7% is an excellent rate, it could be hard to beat or match that in the future if you try another refi.

This could be in the form of offering to pay the security deposit on their new rental as well as their moving costs.Gail

I learnt a lot about being very careful on how you qualify/disqualify applicants by using my criteria (and a scoring system-I think its makes it very clear cut, if they score X then they qualify, if they don't score X you can give the opportunity to score higher with a double deposit for example, except if there is an automatic disqualifier such as past eviction).

Ask them how much their rent and security deposit is.  

Wells Fargo is a great card because I believe you can deposit up to $10k versus the paltry $300 or $500 you will likely be approved for with the Capital One's of the world. 

But if you want bad Karma, keep the deposit.

See ya later security deposit 

If you do get stuck with it and your tenants don't pay you back, you could withhold it from their security deposit (assuming you gave them a copy of the rules when they signed their lease and incorporated them into the lease).

You might consider a larger deposit and state in the lease that minor maintenance issues and repairs needed due to being damaged are the company's responsibility.  

If you get under contract for 30,000 and you mark it up to 40,000 if somebody is interested into that $40,000 then what you will do is say “You are interested in this property, give us a deposit for a $1000, we’ll put it in an escrow at the title company.”