I would like to learn more, I listen to podcasts and YouTube videos about investing almost everyday so I know some information, I have just yet to apply it.

My loss on this deal was the cost per lead, my time, the inspection report, etc.

You can find all three at MeetUp.com.Deal Seekers lead by @Jay Orlauski.

It automatically adjust for day of the week, seasonality, events, and lead time to give me the best pricing.

I am concerned about calling them back and letting them know we want them out regardless as this could lead to property damage.

You could always start marketing for deals (using mailing / list services) and then partner with another local investor who can take has the bandwidth to take on your inbound leads and can handle negotiations, acquisition/exit strategies, contract administration, etc. in exchange for a profit split.

I got involved in Fixing and Flipping houses as a result of the leads I got from my "refinancing" clients way back when.

I assumed all buildings in MA were smoke free.I called the prior management/HOA and they essentially told me I have no recourse even though it lead to my tenants leaving my rental.Any advice on action I can move forward with would be appreciated.

Checking local code requirements is essential.A comparison of a residential (1-4 unit) property to an apartment block is mis-leading.  

The reason that I’d start there is that it could lead you to your answer of duplex vs. 12-plex.There are more than a few markets where you couldn’t pay me to own a property...