I also purchase for long term buy and hold so even if there was a pullback in the next couple of years due to something unforeseen then it wouldn't matter to me as much....I like dollar cost averaging in real estate and I'm never really concerned too much on where we are in a cycle...regardless of cycles as well, even in the best of times I would never suggest that anyone buy real estate if they don't plan on holding for at least 5 to 7+ years

I ended up with a rehab around 42k, which included unforeseen items like a new heating system, under-estimating appliance costs, landscaping issues, higher than expected electric costs, etc.

@Carl HoffmannThere are ways of getting into properties with less than 20% but the buyer should still have a solid reserve fund for the unforeseen and unavoidable problems that always happen with rental real estate.

Other than something completely unforeseen and catastrophic there is not fundamental reason for it to crash.

If so, having cash flow negative assets or assets that one unforeseen expense wipes our years of cash flow is not an investment, it is a monthly bill like your cell phone or utilities.If you are banking on appreciation, that is a different game, and I would be looking at single family flips to get in and out quickly, but there are clearly a lot of risks associated with those as well.

Any unforeseen spending could end up with you leaving money in the property.

So far, on the properties I’ve analyzed house hacking may lower my monthly housing costs by ~200-400$/month (although I do realize this could quickly be negated by maintenance costs and unforeseen repairs); my train of thought is that I would still be contributing that 36k towards an asset that is building equity (while someone else also helps me achieve that), instead of paying it in rent with no return.

There will not be many unforeseen surprises as long as you buy a Condo in the right location and that has a well managed Association with a significant amount in reserves.  

Unforeseen pitfalls?

Cash flow is not the primary motive in this case, but I look for it to provide a buffer for unforeseen events, rent compression, etc.