Additionally, you and the seller agreed to handle and shortfall(Yes keep in mind you could have been shortchanged as well) or excess will be handled outside of closing.So, if you owe the money you should pay it just as you would expect the same. 

Do the investor or original owner have an opportunity to recoup these excess funds?

Have you had any issue with crime or excessive damage to the place?

I believe Evolve provides a service like this, which they charge 10% for, which is excessive to me.  

In year 1 you get to take an additional $13,500 ($15,000 - $1,500) of excess depreciation.

Keep in mind, some states will charge a transfer tax when you change the title over (which can get a bit pricey).While I'm a big proponent of cutting out excess fees for things I can do myself(i.e. setting up LLCs), however, in this situation, I would consider using a lawyer to make sure this is set up correctly.There is a good YouTube video of the overall structure which you are describing by Clint Coons using a holding company with child LLCs.  

I'd like to say a big fat "You're welcome" to the BP community for introducing one of the finest gentleman the real estate investment world has seen 🙏👍Here a you go mate - https://www.biggerpockets.com/forums/55/topics/114811-pleasu...And yes, 38,000+ thousand posts later I can say "it's working" haha

HELOCs if they own a primary......cash out refinance if they own a primary.Borrow from family.Side hustle for a year....uber/lyft, deliver pizza, Amazon warehouse, PM, cleanout services, garage sale item flips(Gary V style)Medical Research....some pay $800 or more for simple vaccine research..some pay $5000 for a week of in patient testing.Trade down cars....flip cars.....saw a guy the other day on youtube flipping riding lawn mowers.Selling all their excess on FB Marketplace and ebay.

Always by excess product (box or 2 or minimum 5% extra) for IF/When damage occurs.

This implies that hands off ADU additions start off with a negative position, often in excess of $50k negative position.