We have an amicable relationship and I've been very generous with them on other fronts.

This gives you bonus density of up to 50% when you submit plans to a type 2 design review with BDS. 

She was generous with her time and money. 

It will rent out for $1050/month.I think you're being too generous paying $650/month in interest.

I wanted to get another opinion first.So duplexes in a c class area here run about 130 to 150kI could rent the one side as long as it is in good condition for around 8 to 900.I was thinking we should throw around 100k down that should give us a morgage taxes and insurance around 500 monthly enough to raise a family on her income alone all while not having to count on the rent so we can just treat it as a bonus and use it for more investing.Would you say that would be a large enough down payment?

The other bonus is you can get a 30 year term on the TSP loan if it's being used to help buy a primary residence.

The comparison to the other three properties (no ADUs) i was given $55,000 bonus but they drug down the appraisal. 

Inexpensive as well which is an added bonus.

I’m certainly not counting on appreciation at all it’s just a bonus as usual.  

One can only wish all gurus were as generous as BP.