I have not read the book but I have done many sub 2's over the decades and for us it was just a standard purchase contract and when it says additional terms we just described that we were taking title subject to the existing debt or which debt would remain on title.

just use homes.com and the AVM from 4 appraisal company usually has 1 standard deviation with zEstimate is in the middle.The accuracy really depends on the object property location and the sample.

I quit my day job as an Electrical Engineer from buying tax liens and turning them into mostly passive LTR's.Yes their are big risks, takes a lot of research, a lot of cash to increase your odds and it is much more difficult now because more people are doing it and driving up the auction priced.I typically get 2 or 3 more houses every year from the previous years tax lien auction.I do not have to foreclose to get my tax deed on unredeemed liens.

This is still a very tricky area for lenders as there are not many "industry-standard" tried and true rules - many DSCR Lenders and buyers of these loans are still wary of the SRO model - that being said, it is a lot easier and more flexible to underwrite on an acquisition if you are buying and the property could be utilized as a LTR / MTR or STR as that allows for a more tailored projection (as long as the property doesn't have unique or altered characteristics that would require it to be a SRO / MTR)

The attorney doesn't have a standard commercial lease or group home lease.  

If they are insuring the property in its current state, it's likely that a new buyer will also be able to obtain insurance without trouble.As for the mortgage aspect, the key factor will be ensuring that the house, including the patio "room" and its roof, meets all local building codes and standards.

My purpose for the HELOC is to get into a property without having a home sale contingency to increase my odds of the offer getting accepted.

Many places, such as California, Florida, etc are experiencing a significant increase in insurance cost.

I  am looking for positive cash flow with this investment,  locations with a propensity to increase in value & friendly landlord laws. 

Because it's a family, my plan is to increase their rent each year until at market average.