One person will tell you how you should take advantage of the reduced interest rates that an adjustable rate mortgage (ARM) offers.

As a buyer you need to understand what an arms length transaction is,that you will typically have a 30 day deed restriction and at times a 120 day deed restriction if selling for more than 120% of purchase price. 

Educating yourself is the best tool you can arm yourself with.  

Depends on your goals there.IMO, if the seller ignored something as large as a foundation wall needing replacement and you already sense there may be other deferred maintenance that was ignored, I would want a larger margin of safety than being all-in at retail value after this major repair with still more work to do.

In the BRRRR strategy is taking a 5/7 yr ARM as the first loan before doing the renovation and refi a benefit or does it not matter when you need to take a loan to start? 

There is some argument about this where the guardian, trustee or executor is an individual "within arms length" of the property owner, not sure if it's fully litigated yet or not, I'm not an attorney.  

While I expect a lot of owners are coming up on refi in the area due to the popularity of 5/15 ARMs when lots of properties last changed hands, a year ago I sold the first property I ever purchased, a 20-unit Class B in College Station, to a family office from NYC... its not like there isn't competition in the area.   

For his safety and my own sanity, I have to do something about this.

My mil has excellent credit, 800+, with no debt.Any ideas on how make this happen.Heloc would be great, but the 15 year term makes the payment too hight.A 3-1 ARM would work, with co-signer, as we would refi after the second year with solid rental history adding to my mil's income so she would qualify at that time.Below are some quick numbers for this project$180k - ADU Budget$142k - Current mortgage$942 - Current monthly mortgage$585k - Current Value of home/property (no including basement refinish or ADU/Garage)$1800 - market rent on ADU$500 - current walkout basement rent ($1200 market)$2200 - mil's fixed budget (PERA retirementThoughts?

Cash out now and lock the current rate in, as opposed to doing the cash out in a few years (subject to that rate being X% higher) or getting a HELOC that's an ARM (and subject to that rate being X% higher).