What kind of return you can accept depends wholly on you.

Well said Jordan, it's not as common in this market to have an ADU but there are some out there.

I definitely prefer to be an asset and not the kind of small business person that doesn't enrich or contribute. 

Google Sheets or any kind of spreadsheet will work just fine.

I'm an IT Consulting guy by day & RE investor by night so getting into the details of all of the technology offerings, how they integrate, which capabilities overlap/don't, where integrated value sits, etc. exposes my nerdiness/love for this kind of stuff.

However, these are the ones most commonly used:Five-of-Ten-Year Test: You must have materially participated in the activity for any five of the past ten years.500-Hour Test: You must have materially participated in the activity or activities for 500 hours in the current tax year.Step 3: Calculation your participation hoursEnsure you are tracking your participation hours.

Would some kind of deal like this ever make sense to you?

Refinancing after reno's are completed with a DSCR is a common great strategy. 

You asked about buying older properties and the biggest issues I have found is that roofs need to be replaced, HVAC needs servicing/replaced, and sometimes there are foundational issues (not super common). 

Common fees will include a set-up fee, a leasing fee for each turnover or a lease renewal fee, marking up maintenance, retaining late fees, and more.