Given your first line - "We are FIRE" - I would say do NOT do it.
Why? The downside is that the house can *cost you money* - worse than going to zero. If you get some bad luck, it can take years before it begins turning a profit, all the while being difficult to sell at a price that allows you to escape.
You say "a hobby" - that's fine, til you get sink holes or some stupid thing that the insurance won't cover.
Will it happen to you? Maybe, maybe not. You could buy, and double your money in 5-10 years, or have a great tenant that stays put for 15, never calling you etc etc. But the converse is possible - a string of bad tenants that break things, leave early, etc.
Don't get me wrong, I am a landlord, and it can be good - find the right property and the right manager and you *should* be just dandy.
But if you are *already* FIRE - why take the risk? The worst a diversified ETF can do is go to zero, and the chances of that are pretty much the same - zero.
(UNLESS you want to become a land baron, in which case the risk is spread out over many properties, hopefully at least somewhat regionally diversified - in which case you'll be fine - but then why not just buy a REIT?)