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.
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.
He meant that you'd have to start fathering children at 14 so that you could have 4 of them under 18 by the time you turn 18, which would be the age for military service.
In IOT, the "s" stands for security.