On the other hand, I read somewhere that rules can't be added or changed if they would substantially modify the lease or the like.   

A smart Savvy businessman like yourself bought the note at a substantial discount and this is your chance to cash in on the spread early. 

If they decline to share, that is a red flag which would warrant walking away or at a minimum substantially reducing the price instead and basing the offer on your own numbers validated by third parties.

However, I would look for properties that are not in resort areas as the resort properties will all be inflated and the owners very recalcitrant to take substantially less than their imagined value.

This can significantly reduce the capital gains tax if the property is sold shortly after being inherited, as the "gain" may be minimal.This step-up in basis is a crucial aspect of estate planning and can prevent substantial tax burdens for heirs.

Typically in a substantial loss, the lease is terminated automatically, the insurance covers your loss and the tenant is on their own for their losses including loss of housing. 

Each realtor here backs their market with substantial data, historical trends, and extensive experience.

There isn't a one-size-fits-all solution as you mention, but I would be sure that this is something that you see as sustainable due to the substantial up-front investment that it requires from the outlay.

Your participation in the activity for the tax year constitutes substantially all of the participation in such activity of all individuals (including individuals who are not owners of interests in the activity) for such year.2.

Spend more time then anyone else doing all substantial services.