My questions are vague to get a broad range of answers and learn.

What he fails to tell people is that your "income" is generally defined as your Adjusted Gross Income or AGI. 

Before you make a choice, clearly define your long term goals. 

However, I wouldn’t define your current situation as being “stuck” as you wrote because you said that you’d have $120K-$180K if you sold.

Those areas are all very diffent, narrow down and your search and better define your criteria.

The bank has said it is a Line of Credit, but hasn't defined any sort of specific cap. 

Define what's important to you as the buyer in the negotiation.

QIP (qualified improvement property) defined by IRS code section168(e)(6) as “any improvement made by the taxpayer to an interior portion of a building which is nonresidential real property if such improvement is placed in service after the date such building was first placed in service.”The intent of the TCJA was to treat QIP as 15 year property.

But all in all I would say define your ideal use, check compatibility with zoning and get a phase 1.

. $25-30/sf for a lower end refresh.I have not designed the garage space for the ADU yet, but when I do define the scope, it will include all new electrical, plumbing, HVAC, custom windows, insulation, 1 full kitchen and 1 full bath, exterior paint and a couple of new garage doors.