What is described here (buying a chain of properties year to year) is unlikely for most people. You can’t use rental income when calculating your debt to income ratio. Unless you have a massive income or an equally massive pile of cash, you are going to quickly run out of lenders willing to lend to you in your entirely over-levered position. Also, you have to stay in a home for a certain number of years for it to be considered a “primary residence” and therefor able to be mortgaged with a low down payment. Otherwise in each transaction you’ll have to come up with 25-30% down.