You would obviously be doing wholesaling so you need to be studying Wholesale (Double Closing and Assignment of Contracts), Creative Financing (Lease Options, Subject to's, and How to make creative financing offers).As far as finding investors...

Read thru BP on this subject.

"The best rent" is very subjective, so the answer is, "It depends." 

Several options, purchase subject to existing mortgage and keep the equity, execute a MLO (master lease option) and generate gross income above and beyond costs for cash flow with the option to purchase if the value increases, purchase cash.

You have to include the interest received on Schedule B and if you are paying interest you will be able to deduct subject to itemizing on Schedule A.

Any liens that occur after your loan would be the responsibility of the borrower and would be subject to your loan.

Mark,Did you purchase this property subject to and then wrap it to the current owner?  

You'd be subject to the banks due on sale clause for the loan.4.

Any room rental use not conforming to these conditions shall be considered a boardinghouse, lodging house, hotel or motel, as applicable, and shall be subject to the requirements for that use.A. 

A couple of books to read on the subject that are really good, Garret Sutton who is Robert Kiyosakis "Rich Dad Poor Dad" asset protection attorney- has wrote several books and just recently released a book that is new.