While I'm sure sites like Craigslist make for good hunting grounds for sourcing sales staff, I'd recommend you rather hire someone you know who understands your business model and, more importantly, believes in its long-term viability. Your salesman needs to be proactive, and there's no better driver than having a shared vision.
With regards to compensation, you're basically saying "Hey, I don't have the money to pay you market-competitive rates right now, but I will one day, so in the mean time, I'll offer you above-average commission until I can afford to pay you a fair rate."
This sounds like a good deal to your salesman, but bear in mind that he is taking on up-front risk, because whilst his commission-rate will be above-average, given the low sales volumes of your software, his actual earnings will still be relatively low. Therefore he should be compensated for the up-front risk he is taking on by being rewarded with above-average commission / bonuses after he has reached market-competitive earnings (but not indefinitely), otherwise he has no incentive to take the risk of joining you.
What should his above-average compensation be? I would offer him as high a commission fee as you can afford whilst still breaking even (and by breaking even, I literally mean the bear minimum necessary for survival). Then once your revenue is high enough so that you can afford to pay him a market-competitive rate, I'd continue to pay him above-average commission rates for a little while longer - perhaps a year - to reward him for his up-front risk. After that you can revise his package accordingly.
The other risk you have to be mindful of is his ability to sell, because if he's a poor salesman, his above-average commission will sap most of what little revenue you're currently earning, without adding much value to your business in the long run. With this in mind, I'd work out a performance-based contract so that you have grounds to let him go should his salesmanship prove ineffective.