I think it’s been quite some time since NFL teams met at college stadiums during the preseason, but in the 1960s it was common practice. The San Francisco 49ers, for example, played many preseason games out of state at various universities.
Here is just one example, from a 1962 tilt against the Minnesota Vikings at Seattle’s Husky Stadium. Or as it was often referred to, the University of Washington Stadium.
If I’m interpreting the stadium diagram on the back of this ticket stub, this seat was almost at midfield. Not too shabby for four bucks!