But if I decide to pay an extra $2,000 per month, in addition to my (dropping month after month) minimum interest-only payment, when the loan is recast to principal and interest, the new payment will be based on the remaining balance ($396,000) spread over 25 years.

If I wanted to spend an hour doing it, I could probably put together a list of at least 50 cities where you can still buy housing for $100/sf or less.

Any additional input would be great.

Example - borrower uses loan to purchase a home in a B or C grade neighborhood for 380k, spends 50k rehabbing primary home, uses 200k to put an ADU in the back, appraisal comes back at 925k. 

If the water bill is $100 a month, increase the price by 20% (or whatever you decide is fair) to compensate you for the time required to split and bill and to cover additional use when tenants squander the utility.

Not sure the cost of this for you but I feel with hot tub and fireplace you already have a lot of warming options and not get much additional revenue.

Seller will be taking a 30k+ loss with this route.325k with 50K down to seller, 3 years of payments $1600/month, and a balloon payment of 215k at the end of 3 years.Benefits to me: (1) 10k less downpayment, (2) with the conventional route, the loan would be at 228k after 3 years of payments, so I will gain additional equity with the 2nd option since I will owe 215k (presumably I will have to refinance at that time).Benefit to seller: she gets over asking price, 50K upfront and $300/month of cash flow.Does this offer and structure sound reasonable?

Because for a certain type renter it’s just SO easy to continue renting fully furnished rather than having to spend $20-40k on furniture; come up with a down payment on a house purchase; and or worry about repairs and maintenance.  

I don’t want to spend a month in a dump.  

You should only consider switching when your current software has a significant flaw or lacks features that force you to spend excessive time on workarounds.