You will find that (properly screened) Section 8 tenants can be far more appreciative of having a good Landord than a lot of cash tenants.Looks like your deal comes out to about $29K per door.

Percentages are great when properly used and understood, but they can also be tricky. 20% on a $100k property is very different from 20% on $600k.

Agree mostly with @Yoann DoratIn our opinion, you can do Class C remotely, it's not easy, but NOT Class D.80%+ of property management can be done from anywhere you can get an internet connection - once you set up the proper systems. 

I’m even willing to make the payments under the gamble of never getting it refunded, if I can get proper documentation. 

Appraisers already have a tough time properly valuating ADU's since they are fairly new and they do not have enough comps to go off of typically.

The contractor needs to either be properly educated on the 203k or have verifiable experience with the 203k.

These folks are amazing to work with and they want YOU (the reader) to do things properly. 

Some windows don’t open or close properly.

I don't trust that tenants will care for it properly.  

The promissory note is almost useless without a corresponding mortgage to create a lien on the property.There's also no reason the title company shouldn't record it if done properly.