But say you have two identical houses next to each other.

One is paid off, one has a loan.

The rule of thumb is value/10/12. So a $100,000 house should bring $10,000 a year, apex $800 a month.

The house next door with a mortgage, costs $120,000 even though it’s actual value is $100K. Why would anyone pay $1000 to rent there the same house in contrast with $800 the real value?

And you are saying it should make even 10%-15% on top of all that? Something is off here.