That’s normal. The idea is you buy the house with a mortgage to then lease (let) out to tenants. The tenants then pay you rent equal to the mortgage plus a bit extra on top, which you use to pay the mortgage and make a profit.

I think he might be referencing those “I’m a Mac. And I’m a PC” commercials

Mineral oil supposedly. Do your own research since it’s your kid, but it’s considered food safe here. Food grade mineral oil is used on knives and cutting boards regularly.