We are helping with his accounting, business valuation, and exit.

Cannot be a (positive) statistic if you're not accounted for.If issues arise, it's likely the original subto buyer didn't cover their blind spots and are borderline if not entirely predatory.

I recommend that you speak with a real estate accountant to see if you will benefit from a cost segregation first. 

I did find a CU that offers that product but they don't take into account the rental income from the other units.

When they move out, I can access their account to charge for cleaning and repairs.

Brett, can you add to this DST "trust account", ie if I sell multiple properties in 2-4 transactions, can they be maintained in the same trust?

Om rrandom bit of advice: you might be able to get by with 1 high-speed internet account if you use aseries of good Wi-Fi extenders, like Eero. 

We have a partnership entity, so it has to file separately and needs balance sheet accounting.

There are also additional costs of operating and maintaining an LLC, like separate bank accounts, annual report filings, tax filings, etc.2.

Remember, you may be tied up in several houses with little cash, so it is important to think of all possible situations.Who is doing the accounting?