Spend around 2k, buy an 2004 or 2005 (any year would be fine, they are the same bike just different colors) Kawasaki Ninja 250 (27 hp, but can still go 0 to 60 in about 5.5), get 60+ mpg, ride it for a year or two, sell it for the same $2k you spent on buying it. Win + Win
Take the MSF Course prior to bike purchase though if you go that route. Also, don't skimp on gear just because it's 'only' a 50cc bike if you go for something smaller. Falling off a ruckus at 35mph is exactly the same as falling off a ninja 250 at 35 mph...or a BUSA at 35mph for that matter.