I've done the math many others here have as well and no one has shown math that actually makes it beneficial to not have a mortgage for ACA subsidies. If you care to share actual numbers.
I have always been on the side of having a mortgage and keeping my money invested until we started talking about buying a new home recently. I'm getting close to FIRE so I've been analyzing the impact on my FIRE date and was surprised at the results. Since I have a spreadsheet of possible budgets with/without both subsidies and a mortgage, I plugged them into CFiresim for comparison. Below are the inputs that I used:
Current Savings: $
655k $599k
Retirement years: 2021-2061
Asset Allocation 80% stocks/20% bonds
additional savings 2018-2020: $60k
House purchase in 2021
30K down payment vs 150k cash purchase
Expenses in both scenarios include ACA subsidized healthcare & taxes. The 11k difference is from the mortgage expense, less subsidized healthcare and resulting higher taxes.
with mortgage: $37k
(in 2051 reduced spending because of mortgage payoff $11k)
cash purchase: $26k
cash purchase: 92.31% success
mortgage:
78.85% success. 92.31% success when treating P&I as non-inflationary.
ETA: fixed a typo in the current porfolio balance and changed the mortgage success ration when not adjusting for inlfation of P&I.