Steve Jobs’ First Device Allowed Illegal Free Phone Service
todayifoundout.com
todayifoundout.com
(tl;dr: Wozniak helped Jobs finish a difficult piece of work Jobs was doing for Atari, in exchange for 50% of the payment Jobs was getting from the client. Jobs got paid $5,000. He told Wozniak that he'd gotten paid $700, and hence Wozniak's cut was $350, rather than the $2,500 it should have been.)
I am sure there are many more sources out there.
Slightly clarification to OC’s remarks. The original contract was for $700 (so Jobs didn’t lie there). However, what Jobs kept secret is that there was a substantial bonus for reducing the amount of chips needed. Wozniak was specially good at optimizing the amount of chips in a circuit so the end design used substantially fewer chips and hence the bonus was much bigger than the amount agreed before.