[Scottendo]

There is no evidence to support the theory that the robin egg blue Rhapsody belongs to TSIII.

There are tons and tons of missions throughout the GTA series that spawns certain parked cars for you to use near the mission start just incase you don't have a car.

Some do apparantly belong to the mission provider, but there is no line of dialogue or implication that he owns the car. It only shows up in one mission, and it's not even parked infront of the building. It's near the Libertonian.

[SoT_Agent]

Well I'm not sure that Stubbsy boy drives a Raphsody,but to answer you'r question I believe that he's filthy rich,but ya' know you have lots of money,but you want more,so maybe he's too greedy and he just drives that car.