depends, how much traffic do you have right now and how much revenue are you generating through parking....
check on the affiliate programs of the broker power houses, Merryl Lynch, Price Waterhouse Coopers, etc. there are tons of them out there, i'm sure they have something in place for lead generation, sales assist.
once you know what the revenue COULD be from there, i'd calculate where the better chances are to make this domain a "golden" one and take it from there,..leave it parked or make it a mini site.