As was mentioned, the idea is to increase living space.  

Sometimes you just need accountability.I recommend you join the local Real Estate Investors Association (REIA) & free Meetups to be around like-minded individuals.In Oklahoma City, we are a tight group of investors and collogues.

Sounds like you've got the right background to become very successful in the multifamily space. 

I have a double level garage that is pretty new and has about 750 sq feet of living space.  

There is a wide range of owner occupant and investor buyers, so I wouldn't focus too tightly on one niche when you get started.

A listing agent provided him with a brochure stating the house had 15,000 square feet of living space, but county records said the residence actually was only 9,434 square feet.

I ask a number of questions like what is space rent, what are other expenses like garbage, water, and electricity.

Little tight on the numbers but you are doing more than most!

I think you can certainly find some single families to fix and flip in Lowell, but the multifamily market is very tight.

But they are tight & I don't make alot after I pay my guys.