You still need a custodian similar to the SDIRA, but you can function as the Plan Administer of your Solo 401K Retirement Plan. 

There are markets that function as drive-trough corridors where bookings are 1-2 night stays, 12 months a year.

LVP flooring, solid paint, functional kitchens.

Buy a functional but very dated "estate" type property do a mostly cosmetic rehab and resell. 

The most accurate or cleanest method is one bank account per LLC, but that is tough if you are solo with 20 properties and do not have a full back office function for each.

For repairs that are critical for habitability, it makes sense to take care of them promptly, while other damages can often be addressed after they move out with deductions from the security deposit.

Once you have a short list, get an account with each one and run them through the wringer to see how they really function.

Her declining health and memory - This is the most critical factor.

It's true that there is functionality in there which gives you more - access to records, owner details, detailed history etc, but really honestly for most investors, using zillow/redfin and working with a great agent is going to all you need.

For B-/C+, I would think function over form.