Looking to flip between Prince William and Culpepper Counties at the momentSo you are mixing two issues.

The best value for your money would be in Prince George's County, Maryland. 

With Prince George's County much of the crime is along the DC boarder.

I'm not sure eotr has that much upside left as compared to Prince George's or Montgomery county, outside of Historic Anacostia most of the areas eotr are very suburban and not that walkable so its hard for me to see them going much higher at least compared to other cheap walkable areas in Pg or moco.

As @Marshall M. noted, your budget is also a factor.If I had to generalize, I'd say that many of my clients find investment properties with good returns just outside of Fairfax County, in both Loudoun and Prince William Counties.

Make sure you warn him that the Nigerian Prince isn't really going to send him a fortune.

Prince Georges County has 1,577.

@Owen ThorntonAt 16 you may want to start with some character building books like “7 Habits of successful people” and “The little Prince” and for the same reason i would stay away for a few years from “The Prince”, “The art of war” and “The art of the deal” On a lighter vain, I just turned 60 and as teenager I read novels with very valuable business lessons :HotelWheels Rich Man, Poor ManThe GodfatherI would love to hear about more modern novels with business lessons.

Theres a huge tech community emerging in the Dulles area. https://www.washingtonpost.com/news/business/wp/2018/06/22/feature/forget-silicon-valley-the-dulles-tech-corridor-is-cultivating-companies-that-break-the-mold/With DC and Northern Virginia booming I see some serious upside in towns in Fairfax county(VA), Prince Williams County(VA) and like what Russel said western towns in Prince Georges county Maryland.

Extend your search out into Prince William County, Fauquier, and down I-95 toward Stafford in NOVA.