Slightly confused by what you want here.
Ferrari Pace car -
Don't sell cars, It is a pain trying to get them back again.
There are several Seasonal races which will generate a large sum of credits in a few game days.
If you have half decent BSpec drivers you could get them to earn you cash on your PS3 (I think there are a few BSpec seasonal events.) That you can set the up, and leave them to win you some credits while you do something in real life (Make dinner, Tidy up, Paint the Fence, Wax the car...)
Stalking - no - Just easier to make sure you were able to borrow the car. (You can check a players Log to see what cars they change into and what races they have won and cars they have bought.)
Pace car - Do you mean the 1967 P4 330 Sportscar? If so you can win that in the normal ASpec/Bspec events... I think it is one of the Endurace races.