If you want to quote out high efficiency boilers for six Tripple deckers for example requiring installation of separate gas, meters etc. etc. - that might be a situation where you would want to work with a contractor directly because you would have lots of different options with widely varying costs.

I have a second condo property where the water quality became unacceptable (PFAS) so I put a filter on the sink and make people aware the fridge water no longer works.

For example, most Developers in the Seattle area are taking many properties and turning them to condos since that is a booming market with high rental rates And sometimes more conveniently built and accommodating then a SFH.

90% is pretty high.

I'm in New York but the prices (at least downstate) are much too high for me to make my first deal so looking more upstate and out of state. 

BiggerPockets also has a calculator to analyze deals, and I highly recommend you start this as soon as possible, even if you are not ready to buy.

The rates are high right now but these loans are limited based on cashflow so you cant take a loan that costs more than you're receiving in rental income.

Are their listings detailed with good-quality photos?

If prices are too high people will just go elsewhere.

Since the contributions have to come from the business income (PM biz) it’s not likely you’ll come close to taking advantage of the high contribution limits of a Solo 401k.