I am buying a property on contract for Deed. How do I know the seller is taking the monthly installments and paying the mortgage? What if he is not and lets the bank take over the property? Do I have any rights then? What if the seller still owes more than what I agreed to pay for the property?

You can record the contract with the county recorder of deeds. This will help ensure that the property can't be sold out from under you.

You can't know whether he's paying the mortgage or whether the balance will be paid, unless you put it into the contract that he shows you the mortgage statements.

As to what other protections you have, read the contract. Everything should be spelled out in the contract. If the seller is not able to convey clear title when you fulfill your end of the contract, you may have to sue them.

Do you have any reason to believe this might be the case?