Although it is a short timeframe, I'll ask about their depreciation schedule and will consult with my tax advisor.

Nevertheless, continue monitoring the cracks, and if things progress, consult a structural engineer.

Consider defining clear roles, ownership percentages, and responsibilities upfront, and ensure you’re protected if the partnership doesn’t work out.Since you already own properties, it might be worth consulting a CPA who specializes in real estate for advice on tax strategies specific to your situation.

Of course, we'll be looking to consult with a CPA on this!

Then I would seek a legal consultation from a real estate attorney to assist in evicting them if they will not leave (we have a few great attorneys we work with in the area). 

DSCR/hard money are non owner occupy loans.If you decide to do FHA203K for the first home - a 203K consultant/inspector will be required for the standard 203k loan, you will unlikely be able to serve as GC and you sign a 1 year occupany affidavit.

Who is the right person to consult about this? 

We consulted with a designer once, but saw it as no value based on what we had already done ourselves.

I don't have any specifics but as someone who is into tech, accounting/finance, and a consultant to grow businesses.

You can use TurboTax to handle these calculations, but if you’re unsure about expense allocation or depreciation, consulting a CPA can help maximize deductions and ensure accuracy.