@Gaurav Mehta in general, the cities in bay area are loosing up the rule for ADU. 

Getting a letter from you reminding them of the day they stand to loose their home is not going to increase their motivation to sell to you.What might help is for you to let them know that selling their home to you is easy.

You are entitled to hold one such insured mortgage at a time - if you move from that property and wish to buy a new home with a high-ratio mortgage, you are required to bring your first property to an LTV of 80%.That said, there are folks who intentionally, or through the loose diligence of underwriters, manage to get more than one 95% LTV mortgage.  

One thing to note when looking at the individual markets, you can make or loose money in any market.

It's like a blackhole - once it's starts it's nearly impossible for these places to reverse the trends - a few places in KS have gotten better - Dodge City, Garden City, Hays - they hang on and are relatively "progressive" (I use that term loosely) compared to their other rural neighboring cities) and have found a way to survive and somewhat thrive in today's society.  

Would it just be better to do a cash out refinance for my equity instead of using a HELOC so I’m not loosing 6% on every house I buy until I can refinance out of that loan?

You're not in limbo, she signed a lease and is bound to it (except she didn't get quiet enjoyment of the property and you haven't moved to evict him for causing disturbances), so she may have a right to move out.

I've got a SFH in a great school zone that's loosing it's long term tenant soon.

Now you also loose your homeowners insurance because no body wants to underwrite!  

Most recently, I was dinged for a closet that didn’t latch when closed, peeling / cracked ceiling, loose floor boards and junk piled on the back porch.