buying a car with tourist visa

Almost certainly, you have to pay tenencia, insure it and plate it according to the laws of the state you buy it in.  Do you expect to take it back to the US and plate it and insure there?  You'll have the EPA and DOT to contend with, I think.
http://rollybrook.com/buying_a_car.htm#Dealer

gudgrief wrote:

Almost certainly, you have to pay tenencia, insure it and plate it according to the laws of the state you buy it in.  Do you expect to take it back to the US and plate it and insure there?  You'll have the EPA and DOT to contend with, I think.
http://rollybrook.com/buying_a_car.htm#Dealer

along with exporting it from Mexico and importing it to the US and registering in your state of choice.

I have two Canadian snowbird neighbors with cars but no idea how legal they are.  We are pretty much in the country and Police and Transitos don't bother about much.  In a big city watch out

If they have current local tags, no one is going to bother them.  If they get stopped and the paperwork is not in order, the car might be impounded and they'll never see it again.

How would they plate it as tourist?  It would have to be foreign made with tourist plates already or legally imported with Mexican tags and the proper paperwork.  If you're buying it from another tourist, there's little risk asking Transito or INM.