2) What methods do you use to determine a comfortable number pay the lessor per month while leaving enough  wiggle room to pay mortgage, cover for vacancies, repairs, taxes while having a good cash flow left over with the intent of saving this to use for the 20% down payment when the option is exercised.3) Would you pay for an inspection up front before the contract is signed, or wait until it's time to exercise the option?

You will not be able to know until you are in contract and can get a copy of the title report.

I think payroll and contract services can sometimes pay for the same things on different properties, dependent on whether you have someone full-time or not.

I have a property under contract and was planning on signing the mortgage paperwork yesterday.

If I find one that's reliable I'll let you know :D haha.Best thing you can do is protect yourself via contracts and lien release forms when payment is made.

You 100% cannot I signed contracts

I don't usually put down earnest money until both parties have ratified the contract. 

-We were under contract/mutual on Thursday February 8th-Buyer couldn’t get financing when the lender checked employment.

I understand when a property goes under contract I gain equitable rights.

You have a right to enforce the contract that they signed...since they left the place smoke damaged and didn’t provide documentation, I would charge them the 13 days if I were you.