There are other games like this out there and you can contact those organization for tips.
I used to play "Midnight Challenge" and "Nitto1320" which are drag racing based game where players could buy racing parts by selling magazines or race other players for pick slips and take their cars and money. Nitto1320 also had its own live chat rooms and forums. The above became a full on competition where players could use real money to buy upgraded accounts and parts. The top players in a round won actual prizes.
Everything I am talking about was happening about 5 years ago so I have no idea how complex it is now.
I must say Eric that this can become an impossible to manage and very time intensive endeavor 'edit - for you' without having many mods to support it. Cheating also became rampant as hackers could create digital revenue streams which led to real revenue.