I just watched the episode where the family pays off the mortgage on their house. I was always under the assumption that they built that house themselves, so how did they have a mortgage?

I just watched the episode where the family pays off the mortgage on their house. I was always under the assumption that they built that house themselves, so how did they have a mortgage?

Maybe they got a loan from the bank to get the sawmill started and had to use the house as collateral?