If you're 2 years from retirement, you need the least risky thing possible, which would just be paying down that primary residence. 25 years from retirement, you've got some time and can take some risk, since any bumps in the road will smooth out over the long term.

The primary limitation being what data is actually recorded.

3) Will I continue paying same property tax on primary and new assessed property tax on the "new" ADU ?

My primary contractor fixed it.  

Does the guarantee ever go away in the primary term?

(Loan program, term, credit score, etc) just for hypotheticals, say your looking at a 30 year conventional on your primary residence with 720 credit, rate could be ~4.75-5.125%  FHA is typically a little lower. 

Interesting.I'll conclude by saying this, people will form their own opinions across these platforms, once all the facts are presented.

As @Upen was referring to I didn’t have the interest correct in my analysis due to lack of knowledge of the higher interest rates for portfolio loans compared with owner occupied primary mortgages.

One going out in your primary three buys.That's all it's going to take to break you like a matchstick.

Ok, so as a first time potential seller and novice investor-I just learned that if my I lived in my home for 2 of past 5 years I may not have to pay capital gains when I sell. I bought my two family back in 2008. It h...