@Tyler Speelman pretty common in this area (NJ) but I think depends on location.

Common sense.

That is the ideal scenario for this investment.On a side note, you cannot have a tenant foot the utility cost of other units, that is illegal.

Since they are not common, or in any quantity to any area, they are hard to finance since they are hard to get comps. 

It's a great idea for the right situation.There are two different scenarios in Texas. 1.

If you run 2 scenarios with same inputs but toggle the “extra payment” scenario in an effort to compare, it reduces your 30Y traditional timeline (as expected).

Thats what I would do next and you can really just see what the numbers tell you (and look at different rate/refinance scenarios how it would play out in the next few years)

So, to play “devils advocate” here’s a possible scenario.  

The landlord responded that the lease was not subject to the Rent Adjustment Program since the rental was for “sole use of one or more rooms and shared use of common areas (such as a kitchen) in the residence,” which was a single-family home.In its decision, the court focused on the definition of a “dwelling unit” as used in the exception found in Civil Code section 1954.52(a)(3)(A), which provides that “an owner of residential real property may establish the initial and all subsequent rental rates for a dwelling or a unit about which the following is true…It is alienable separate from the title to any other dwelling unit….” .

They are common sense but many still seem to ignore them.