[EGreg]

Mortgages are a sales tactic

You can make a mathematical transformation to compare Renting with Owning.

O - R + R vs R + X

Own - Rent our your place + Rent somewhere else vs Renting and investing your principal some other way. So reducing you get:

O - R vs X

So owning and renting out a house vs all other investment opportunities, such as Bitcoin. Literally if you rented your house in the last two months and invested the principal into altcoins, you could then own 5 houses!