My Father-in-law was a long time season ticket holder for the Raiders before the Oakland Coliseum was built. The games were played at Laney College in Oakland. I have a stack of old Football cards from when I was a kid. Here is a quote from the back of my Ben Davidson card. "Ben is a construction worker in the off-season".
The players had to have another job as they weren't paid much back in the early days of the NFL. The guys played for the love of the game, not the money.
In action at the Oakland Coliseum.