The paper I bought is institutional and has terms for assignment of rents, but the borrower is long gone and I'll assume no rental agreement in place.

You can never know enough, and the more research you do, the more likely you are to discover any issues BEFORE you start a business partnership– Get professional advice on how to set up a partnership agreementIt might be more expensive to have a professional and well established law firm help you with your Partnership agreement, but it will save you time and money down the road in the case of any disagreements.

I discovered BP a while ago but didn't really get involved until recently.

A number of catalysts caused everything to spin out of control: 1) the market changed (duh) and 2) major construction issues were discovered around the complex.

My thought is that if both tenants read the meters and then supply me with the readings neither could state the readings falsely without their deception immediately being discovered.  

And, you got into part of the work, pulled a wall down and discover that the addition a previous owner did was wired improperly and has to be completely rewired.  

"Not required" because you don't have to do it per the relevant IRS rules/laws/guidelines/policies, or "not required" because the IRS is unlikely to ever discover that you broke this rule and if they do the consequences are minimal compared to the benefits, or "not required" because there's no way in hell the IRS could ever have any way of discovering it in a million years?

Yes, if the borrower had made threats to the lender (which would have been recorded as all institutional lender's phones are tapped) then the lender would have cause to  ask for a restraining order.

You also need to talk to financial institutions regarding Hard Money Loans.  

When we took over, all the units were occupied, but we soon discovered that occupancy rate and positive cash flow are not necessarily related.