1. He will stay motivated, even when you run of cash and motivation.
2. He is in it for more than the money and the friendship, but because he actually believes in the idea
3. When there is a disagreement, he will allow you to make the final decision, and not decide to leave
Don't go 50-50, because this guy may be a good coder, but he's just a coder. The ideas are yours. Later you may bring in 2-3 other people, what percentage do they get then?
I think your idea of a salary at the start + 10% to 15% is more reasonable. Give him an option to get to 20% if he does some particular stuff.
But take him on! A one man show is really tough, particular later when marketing becomes much more important. You'll need someone hacking away while you market.
An idea is not worth much without execution, but the actual code-writing is a little part of the execution. If one has a bit of an ability to code and some money, then one can 'manage' the development using cheap freelancers.
Giving up 50% to a guy who just will do the coding at the start is too much. But if he is good at marketing, analysis, idea bringing and all the other stuff that take a company over the first year, then one can give him 50.
1. He will stay motivated, even when you run of cash and motivation.
2. He is in it for more than the money and the friendship, but because he actually believes in the idea
3. When there is a disagreement, he will allow you to make the final decision, and not decide to leave
Don't go 50-50, because this guy may be a good coder, but he's just a coder. The ideas are yours. Later you may bring in 2-3 other people, what percentage do they get then?
I think your idea of a salary at the start + 10% to 15% is more reasonable. Give him an option to get to 20% if he does some particular stuff.
But take him on! A one man show is really tough, particular later when marketing becomes much more important. You'll need someone hacking away while you market.