agree with tom_rath (upmodded). you shouldn't give out equity if you don't know the value of what the other party is bringing to the table. And if sales do not cover their own cost you are losing money having him work for you.
Also, never forget that issuing equity takes time and money for handling the lawyer, accountant, etc. It also significantly reduces your flexibility down the road if you need to reincorporate, transfer assets, etc. And it is easy for things to get messy if there are problems. You want to keep your organization as flexible as possible.
If I were in your shoes I'd offer an excellent commission on sales and give your friend an option to purchase equity in the company up to a set amount at some reasonable valuation. Treat your friend's required investment the same way you would treat an investor at this stage. If he helps the company grow your agreement becomes a very good deal.