Sooo he did not talk terms, he did not sign anything, and now he is complaining? Sad to break it to you buddy, but the real world is not fair game, and you got played.
By the tone you take with your statement, you're saying it's okay to exploit people this way. It's not. Period.
Maybe that's a sign not to join though.
Unfortunately, when enough people wriggle, the founders get their act together and stop behaving that way when they really know they need someone and can't do it alone... by which time, they get someone else that didn't have to fight to get things done right and you missed out because the timing was wrong. So it's a bit of a double edged sword in that respect.
Further, if he was an employee, in many countries, it's illegal to work for free or "defer" pay until there's cash in hand. And it sounds unlikely he was a contractor as there is no mention of invoicing or similar.
Getting rights and responsibilities in writing protects everyone involved. And do it before cash and emotions are involved.