Helping your son is one thing but, if he's not helping himself as well, it just becomes a never ending cycle.
I have an 18 year old. I want her to save her money and I want her to understand that the real world DOES NOT cut you a break. She pays a small rental fee($100) to live with me. She doesn't have to pay for utilities, however she does have to help keep the house clean.
We said we would help her get a car and would match her up to $1000.
She works at the supermarket deli for $8 an hour. Within 2 months she saved enough to buy a car and pay insurance on it.
At 22 your son should understand that sometimes what you WANT is not always the thing you NEED.
Stop driving him unless he pays for the gas. Stop letting him live at home for free. He'll figure out that his job is necessary for him to live at home and his freedom depends on getting his own car.
Part of our job is to prepare our children to survive in the world without us. We can help as long as it is help and not just sheltering them from reality.
Good luck,I know it's a hard job when you love them so much.