We all should all know one of the biggest risks in FIRE is inflation.
if you're on some kind of fixed income, inflation will eat away your purchasing power if your stash doesn't more than keep pace with it.
One defense is to buy a long term anti-bond. A liability that stays nominally fixed and will gradually erode in value.in exchange, the proceeds are invested in growth such as stocks or real estate.
An the easiest way to get that is - if you live in the USA at least - a 30 year fixed rate mortgage. So in the process of buying a house we will get an 80% mortgage fixed at around 4.1%, 3% posttax. This debt will shrink over time, and only represents less than 20% of the stash, but it will help take the sting out of long term inflation being higher than expected. Plus, this long term rate is being artificially kept low by the fed. This is presumably why few other countries have economies or exchange rates stable enough to offer such products.
Also, its something to get before FIRE, and on a property you can keep for 30 years!
The balance of the loan will be offset by a bigger stash. Partly including rental properties that will throw off way more cash than would be saved by having all that equity in the house.