I bought a place and the seller had to put in a new septic field, rest of it was fine.

A lot of them will only point you in the "right direction" and have you consult with a licensed professional in that field (ie. structural engineer, licensed electrician, plumber etc) if there are any concerns. 

You can outfit as a full unit and still have two separate tenants per say but a master lease would provide the most protection to you when fielding applicants use MA housing court data base to run applicants through to see if they have any prior housing court claims

Most real estate agents interested in investing themselves work in the commercial brokerage field; however there’s no inherent reason an agent interested in residential investments can’t specialize in same.  

The “no closets” comment makes me nervous, as I have been told numerous times by appraisers that a space is only a bedroom if it has a closet and a means of egress.  

That does not work and is only for experienced renovators who know their buy box and know they will always go to the studs and redo everything.Just get out in the field, see every dump on the market, take sneak photos to show to a contractor, and get some investor and contractor friends who will be in the ballpark on the costs.

Through this platform, I have received numerous booking requests and have been able to select those that align with my requirements in rent-controlled San Diego.

I'm not an expert in this field. 

Relying on advice from Layman in the field seems like a very risky way to conduct business.

As most people have mentioned there are numerous ways to invest, and get into the the real estate world.