I will add that oftentimes the fixed costs with installing any kind of pool (fence, pump, permits, excavation etc) are so high that the marginal cost of a plunge pool vs something more standard is relatively small.

We're still seeing a high demand in our area for small private furnished rentals, primarily travelling medical professionals. 

It's saturated now and management fees are high for STR, up to 25 percent.

And while it is not common that you find a $100k industrial building, it is also not impossible, depending on condition you need.But at a high level, there are a few factors at play: everyone needs a place to live.  

Unless you are planning a DST (not sure if SDIRA's can hold this type of investment) which is similar to high rate bond investing depending on the rate of returns. 

If it is a normal 70/30 leveraged property, you may end up subject to tax on 70% of your returns anyways - so cost benefit, is that 30% tax free portion worth the high tax rates paid and additional filing fees to get tax free treatment on the 30%?

This is my second year attending and I highly recommend it for all MTR operators.

Should I be a private lender since rates are so high?

But based on a couple office buildings in the same zip code I pretty familiar with that rent seems high for that class of office.

Given that you're just starting to learn, I would highly recommend talking to lenders and real estate agents in your area.