I also want them to pay for any modifications/adjustments to the space they need for their business, subject to approval by me. - Never done a commercial Loan, what to look for? 

Some Class C buildings can be made into Class B buildings given the right location and modifications/upgrades.Class C buildings are generally between 20-30 years old or even an older renovated property.

There are no accessibility codes for residential housing so the objective should be to find a best house needing the least amount of modifications to meet the tenants needs.

This necessitates expanding slower than most people would like but it helps to prevent your investments from collapsing.

Short sales, not purchases, loan modifications and workouts are not the job of a trustee, it's the note holder or other appointee who calls those shots.

It would just be a note modification. 

High liability potential activities will necessitate different approaches than lower liability potential activities.

I am aware that I with a few small modifications I could do this within the excel sheet I currently have, but I'd prefer to use software if there is something out there that is reasonable.

MODIFICATION.

@Imrana LatifYour plans will be subject to securities regulation and will necessitate the preparing and filing of a prospectus for a private offering of corporate shares (or the selling of units in a private REIT).