Under those conditions, I'm surprised he isn't asking for a decent chunk of equity up-front. You said it yourself: "this guy would need to take a risk." Compensating a risk with a fixed payout is more than a little shitty. Also: think hard about the incentive structure you're building for yourselves here. If he gets equity when a) the startup gets through a second funding round in 6 months, and b) you also decide to continue his employment, the rational thing for you guys to do is ditch him in 5 months and 29 days if the company is going well. If I were him, I'd be really careful about getting into that situation.

You've got to remember that the fact that nobody else is taking a salary is a choice you guys have made, it's down to your personal financial situations, and it's not something you should hold over someone else as a justification for not paying them. Especially if you need him that badly.