If this is your only developer, you should be open to giving away some equity to him. It doesn't have to be more than 5%, and could be considerably less.

Much of this depends on the specifics of your situation: what does your company do, what is your current revenue and burn rate, what are your goals for the company, etc.

I have been through this myself in many scenarios (boot strap, post-series A fundraise, doing-it-myself, and on and on). I've also advised other companies going through these questions. There is no simple answer across the board, it all depends on your situation.

Let me know if you'd like to chat more.