Seven kids? Wow! I hope that you have all your kids' financials set up for their future. There are great products available now for college plans, aside from the 529 plan, CD's and savings accounts.
When it comes to payments, you may want to consider a town house instead of a detached home. You can usually get more space for the price.
If renting a house, make sure that you get everything in writing. If the owner has a mortgage, ask if you can pay the bank directly. Too many owners (without management companies) don't make the payments to the bank and then the renter is left out on the street. If you do pay, do so with checks so that you have proof of payment. If the person requires cash, request paying with a money order or cashier's check/credit card.