Selling a permit is not a criminal offense. The seller cannot be jailed. However, if someone sells a permit and if someone else who doesn't like that person, informs the relevant department, then
1. the person who bought the vehicle under the permit may be asked to pay the full taxes of the vehicle
2. if the person fails to pay the full taxes, the vehicle may be impounded.
I know of one case where the above actually happened.
There is always a risk factor involved in this kind of transactions.