During the offseason they get a small per diem to come in during workouts. Players who haven't made the team and their just for camp fodder get a decent hourly wage.
I had a friend who was a keyboard player in a night club I worked at years back. He was well built and in great shape. He tried out for the Carolina Panthers. He made it to final cuts before being cut. During that summer, he made enough money to pay off his house and buy him and his wife brand new cars. Now this was over 10 years ago. He said he would never do that again. So yeah, even those guys make a good amount of money.