ADUs can significantly enhance your property's value by adding living space that can be used for rental income or as additional living quarters for family members.The increase in value from an ADU can vary widely depending on several factors such as the size, quality, and functionality of the ADU, as well as its integration with the main property.

Most inspectors will know that properties only need to meet whatever the code was when they were built, not current code and they usually explain that properly IME.

You have to properly vet and perform thorough due diligence (which I didn't do a couple years ago when I first jumped in).

For overnight rentals, functionally it is a bedroom.

My suggestion is to build a spreadsheet and include the net cash flow to you for every month of the deal, then use the IRR function to figure out your return. 

As for liablity for a mom and pop landlord I agree do the best you can and have proper insurance..

The function of this guide is to get the reader up to speed quickly on the neighborhoods so you can invest in neighborhoods that meet YOUR investing criteria.

One city near me is checking all garage enclosures, giving nice notice to get them permitted, which they may or may not grant, and if you don't get it properly permitted by December 31, says they will start fining people. 

So you can really get an idea for the market and if a property you are looking at is properly priced!

Sounds like its time to sell since the HOA fee just doubled which usually means the HOA has not been managed properly and failed to build a strong reserve account.