You live in a fairly large town, where the people that pass through are different everyday, and the people who pass through the diner you work in are even more varied. You meet a lot of different people in your town- especially hunters.
So you began saving an extra room in your house for them. A place where they could stay the night and not have to pay anything, because you knew money was usually short with hunters. You thought you could do this because you would never see the same hunter twice, and that it would all be good.
And then the Winchesters came along.