You didn't state where you live, but if it is possible to volunteer for a local sprint car team that would be a great way to start. Most local teams are always looking for help and would be willing to help train. It would be a great way to learn without jumping into the deep end of being a traveler. It will also help with the resume if he decides to go it again next summer as a full-time road warrior.

Finally, after some quick Google research, it looks like at 18 your son can get a CDL license but would not be able to leave the state as a CDL driver until he is 21. If your son does not make it as a crew member at least he would have a trade to fall back on.

https://www.smart-trucking.com/cdl-age-requirements/