Not a single guy with no experience in the field.

I do not have experience with above ground but I believe that would be fine if done tastefully. 

One thing I've learned from my experience is that I do not set hard rules.

I don't have personal experience with it, but when the app was first developed, I contacted the developer and put the app through a fairly robust test usage to see if it's something I would want to recommend to my clients (I'm a CPA).I think the app is great for its intended purpose and I do recommend it to my clients now (and have for about 18 months now). 

What you want is an agent with experience who knows how to negotiate, watch your back, navigate difficult situations, understand contracts and law, provides an objective cross-check, etc.

Any advice or shared experience would be great.

Do you have experience with STR? 

DM me if you want to discuss my experience as either an investor or a lender.Jeff

Rent control in the bay area can be extreme as many areas have rent control in excess of the state mandated rent controlIn general experience RE investors are not choosing to add a single ADU in single family zoned areas.  

We have sent over a few referrals to him and they have given us great feedback when we asked how their experience has been.