It's all worth it if you hit paydirt

Bobby Marks offers "The life of the non-guaranteed NBA player"

A snippet about where it begins -- summer league participation: "...The only compensation that occurs is a per diem (“food money”) of roughly $127 per day, hotel room and travel expenses. What you earn goes towards eating during the day. Players must also sign a waiver to participate, allowing the team not to be liable in case of injury...."