Brian's suggesting of seeking a professional in your area is really the best answer.There are too many variables and not enough information to really answer your question.

These are the biggest X's banks use to deny loans, variable income, no verifiable income or short time on job.

The variable that I don't know how nail down is how much a property will ACTUALLY rent for per month.

Do you have a fixed interest rate on the property now or do you have a variable??

If you have the contract with the home owner, then I am assuming you signed a simple buyer will buy and seller will sell contract.If its through a bank its a full flegged real estate contract with a no assignment clause.Too many variables to go over without knowing more about your contract and deal.

Too many variables out of your control.

Is it variable??

They did include a line item called operating expenses but no lines for taxes, insurance, management fees, or any variable expenses.

What I am also doing, is trying to understand the different variables, in order to fully analyze a deal.

You are in the right place and asking all the right questions.There is quite a bit to learn before you take the plunge and many of them are variable.