My Partners and I have been buying Brooklyn small multi's (2 to 4 Unit buildings) since 1998.We currently own 9 of these buildings in various neighborhoods including Clinton Hill, Bed-Stuy, Windsor Terrace and Ditmas Park.Total Assets would be somewhere between $15 and $20 Million in the portfolio.Every since we bought the first property, which was in Ditmas Park for $340k in 1998, everyone told me it was crazy.I continue to hear how crazy I am to continue to buy every one or two years since 1998.That $340k Property in Ditmas Park is worth $2 Million today.

A good rule of thumb is this:  Be careful and fully understand the risks of "getting in bed with the government". 

The property in question has commercial space on the ground floor with two, 2 bed/1 bath units above.

I did not choose.I selected configurations similar to what they were renting—for example, 3-bed, 2-bath, yard space, etc.I focused on locations where they were currently living.I set rent prices within their budget.SummaryI became successful at real estate investing once I understood that what matters is the tenant segment who occupies the property.

He purchased a relatively inexpensive ($210k), 3 bed 3 bath townhome.

I can’t imagine an ADU would be very beneficial, and most dont have a basement to convert into more bed/baths.

She says she notices it in bed and has to put the bed a certain way (like with head on higher part).This doesn't seem to be enough of a problem where any part is unlivable or that requires immediate attention, but the main jist of this post is, where would I start or what type of business or contractor could I start with to find out about this?

The house is a simple two bed one bath with a garage and a fenced in backyard.

Maybe leave a kayak for guest to use (have them sign waivers in case of accidents).Get some old furniture, some bicycles to loan and make a bed and breakfast!?

We converted an existing shed to a 1 bed 1 bath apartment and now rent out the bigger house for great cash flow.