How does the IRS even find out you buy a car? There’s no federal sales tax. You just pay your state taxes.
If it’s a “nothing fancy” car, maybe a 30k accord or less, and he has a good income, it’s not going to raise any flags with either state or fed.
Bottom line - pay your taxes and you’ll be fine.
I can’t emphasize enough how good a feeling it is to have the title to your own car.