How to pay off loan?

[Dayton Rowe]

This may be a very dumb of obvious answer, but I was reading the book of on real estate investing by Brandon Turner and in chapter 3 when he goes over his first plan I see a problem. He talks about in year one you find a property that is worth 100,000 and get is for 80,000. Assuming the seller is paying for closing costs you will then be required to put 20% down. Now you will then need a loan. I am very new to all of this, but he never mentions how to pay the loan off. I could have overlooked something but I think I just do not understand. Any insight on this?