I'm pretty sure though that the mortgage is a negative when it comes to SORR.
So just say you have 2 million in assets at a 4% WR. So you can spend say 80k per year. You have a mortgage for 1 million. If the market crashes 50% you would have assets of 1 million and just say you have to reduce your spending to 4%. That leaves you with 40k to spend but your mortgage would still have to be serviced with the same amount of money. So if your mortgage costs 20k to service each year that would mean your spending excluding the mortgage drops from 60k to 20k.
If you were choosing between a paid off house worth $1M or getting a mortgage for $1M and investing it then your choice would be between:
- $1M invested and a $40K/yr spend at 4%WR with a paid off house
- $1M +$1M invested and a $40K/yr spend + the mortgage payments
Additionally if your portfolio started at $2M and you are following a 4%WR plan you don't change the WR amount downwards so that it's 4% of the current amount invested should the portfolio drop.
You can look at it like two separate investment accounts. One the standard FIRE account and one the home equity investment account. Since the FIRE account is the same as it would be with a paid off house the SORR is the same as it would be with a paid off house.
So then you are left with the SORR on the home equity account. At the start you have very little equity in the house so the risk is losing a small amount of equity. The mitigation plan would be the same as for FIRE in that a few years worth of bonds could be held to provide protection against a SORR and then either spent or left to be outrun by the equity portion of that account if early returns were not poor.
I ran these numbers in cFIREsim:
- $1M invested 70/30 with 0.1% fees
- 30yrs
- WR $53612/yr [not inflation adjusted] - this is what my mortgage calculator says is 52 weekly payments at 3.49% for $1M borrowed
I get a 98.3% historical success rate compared to the 95.8% for the main FIRE portfolio at 4%WR over 30yrs with same AA. So the mortgage portfolio is less risky than the FIRE portfolio. It also has one additional safety element...namely that you are building equity the whole time so that you could pull more equity out and reinvest it should you feel you are in one of the very few problematic starting years. I don't have any math to simulate that [thinking about it], but I suspect you could take that historical failure rate to zero with that option.
I'll be FIREing with a mortgage and will likely see that mortgage stay in place for the first 15-30yrs of FIRE depending on what happens when we relocate.