Originally Posted by
DallasEsq
I would guess 18 is the minimum, as that is the age when people can accrue points through checking in to a hotel in the US or obtaining a credit card. The hotel, I believe, sets the minimum age for check-in but I don't know of any that allow minors to do so.
I stayed in some at age 15-17 (either for or adjacent to school-related trips; parent had to fax a letter and credit card info or something, but it wasn't a big deal) and I earned points. I had just turned 16 when I stayed at the Sheraton Gunter San Antonio, I think that was my first SPG point-earning activity. I would be surprised if there was a problem opening accounts for even very young kids. That was also a long time ago, things may be different now.