Since you DO live in DC you can make a ton of easy money by getting an '01 FFL' and becoming the only one willing to do Legal Transfers and req'd Background Checks within the District. Just guessing, but your upfront costs may run about $1K for BATF fees and DC permits but that would be recouped pdq at $30-$40 per transfer, or higher if you want since you'd be the sole source of legal handguns in DC (In IL $30 to $40 is the average transfer fee).
IIRC there are currently only four Class 01 FFLs in DC and none will do transfers. One FFL holder is an exec. at the Violence Policy Center (that's a laugher) who got it for "research". That is against BATF regulations and as such, the law. But they'll be busted like ... never.
That is an interesting idea.