Charlotte seems very spread out in terms of neighborhoods and it's difficult to gauge rentals demand in this city as compared to some other metropolitan areas where public transportation is more prevalent.Additionally, what are some good sources to find reliable input assumptions (rental rates, tax rates, vacancy rates, growth rates for rents and house prices) for modeling a deal?

This includes, in this order:  (1) bios, pics and contact information for you (and your partners if you have any); (2) list of your professional team members; (3) detailed description of the kind of property you are looking for, including location, price range, unit%, cap rate, and any other details relevant to your investment thesis, such as good school districts, transport hubs, etc.; and (4) the preliminary due diligence materials you require to underwrite the deal

Public transportation is also all around me.

What should I be aware of, all else being equal (taxes, zoning issues, the area (possible crime, population decline, unemployment rate, economic vehicles, transportation hubs, etc.).

(within subdivision,  parking spaces etc)o  Close to big employers and avoid those sensitive areas.o  Good schooling districts, easy access to public transportation etc.After some extensive research and to satisfy the above said points I have decided to acquire a land to build some rental units.   

Washington area, walking distance to shops and public transportation and 10 minutes or less from downtown.  

There are plenty of people who have jobs that require them to travel often or have jobs that have long commutes via multiple modes of transportation and still have a place they call home when the traveling is done.

The major work needed to make them habitatable is: enclose them by installing windows, frame up a bedroom in one unit, add flooring, kitchen and bath cabinetry, electrical & plumbing fixtures, basic appliances, and one unit would need private egress.   

I don't know how gas prices are but Nyc and Seattle are a dollar a gallon higher than where I live at least, which means paint and transportation costs more.

Everyone above has made great points.. look at it this way .you have a 425.00 rental what is the standard for putting a tenant in a rental  3X rent = gross income .. so tenant is qualified at 1200 a month .. to move in.. minus 425 leaves them 775.00 a month to live on less than 200 a week to pay for UTLS food transportation if any.. your simply getting in many instances the least stable folks in the US.. they have one little upset and they usually do what happens rent does not get paid.. there is a reason these properties trade at those values and rent at those numbers.. its simply not exponential in  a backwards fashion that 425.00 rents are great since they are so low if that makes any sense.like @Jason Hirko  says if you have 100 of them and have all in house management and turn over services you can make a run at it..