Definitely worth properly modelling out both buy and rent scenarios including all related costs, the substantial tax benefits of the mortgage interest deduction

Definitely worth properly modelling out both buy and rent scenarios including all related costs, the substantial tax benefits of the mortgage interest deduction, remembering you are paying down principal in the mortgage payment, and the opportunity cost of the down payment. But when I've done this the cutover point is usually fairly close to where mortgage payment = rent. The other thing that's notable when you model the scenarios is how much of a difference it makes how long you stay in a house given the absurdly high transaction costs of selling in a house in the US. 5% realtor fees! $50k on an SF condo, $75-100k on an SF house.