We did some cosmetic work, installed new kitchens / baths, flooring and painted it.

You need a team because you can no longer DIY everything. 

After 3 months of fruitless negotiations with this person, buyout offers, debt forgiveness, appealing to ethics, etc. we had two moves on the chessboard left.Meanwhile in the bat cave....the string tenant had decided to move their belongings into each of the 5 bedrooms, install their own interior security cameras, fill up the garage and office with their cars and mechanics equipment.  

Something along the lines of "landlord reserves the right to install additional electrical panels and separately meter the electricity...yada yada yada."

I had purchased this condo 2 years ago and it looked like the Seller had just upgraded the bath & kitchen (including installing a new countertop & cabinets), at that time.4) If I’m allowed to deduct their deposit, do I just need a quote for this, or would we actually have to get the work done?

I am no expert but some issues you might want to look out for:- Mold in crawlspace/basement (as well as evidence of running water during storms, we've seen this)- Structural damage/settling (definitely hire an expert on this one)-Improved Electrical/Plumbing (These systems DO have a lifespan and the older systems aren't as reliable as newer ones)- Asbestos Flooring and Tile (Where I am from the removal of this stuff is mandated by law to be done by a licensed professional, no DIY.

It failed HUD inspection because the PM didn't have the furnace or hot water heater installed, and the pipes were froze.

We install low flow Delta toilets and fixtures and that will save you money, but one leak can loose and entire years worth of savings in less than a month. 

The property featured an unimproved accessory dwelling unit (the second unit) that we worked with family friends to DIY renovate and turn into a fully furnished cash flow machine.

(Maybe that professional is the same person.)If you just own two properties and want an easy option for DIY bookkeeping, I recommend Stessa.