What is a Topps Football card that is inexpensive now that will grow to be worth a lot of money?

Thats a crap shoot! You could buy an Adrian Peterson card but it doesnt mean it will be valuable. If he stays healthy and keeps going like he could, then yes it could be very valuable. But thats the same thing with any player. Your best bet would be to buy some cards of players that you think will do something with their careers and then hope for the best!