You have to have a system set up for vetting guests, creating leases and collecting deposits and rents.

Discover, for instance, will deposit the money for your "balance transfer" directly into your checking account, and often has specials for 0% financing for 12 months with 3% up front transfer fee, or 5% financing for 18 months with 0% transfer fee.

Think of all the things that could go wrong and see if the lease addresses them: unauthorized pets or tenants, early termination, security deposit, lease violations, late rent, eviction, lawn maintenance, parking, etc.5.

The lender is stating the following: "we would require a mortgage on the lot in the amount of $90,000.00 when combined with your $50,000.00 deposit would be $140,000.00 down payment apx a 20 percent down payment"Is he saying I need to find another $90,000, or that he will act as the mortgagee on that portion as well? 

What happens to original security deposit from original 12mo lease?

If you send the security deposit disposition to the address they rented from you with ADDRESS SERVICE REQUESTED written in the area between the address block and stamp you'll get a postcard back with the details if the mail is forwarded. 

Tenant decides not to pay and use security deposit for last payment (not allowed).

It good for your tenants and staff, not dealing with bank deposits and cash/checks.  

As the seller, why would you return the deposit?

Are the prorated rents being given to you (along with deposits) or is the seller keeping it?