I understand your reluctance and I suspected that I would have this type of question about salary. I start from the principle that all work deserves payment but given that our project is to free ourselves from the system, you will therefore understand that our desire is to be remunerated with our coin.
If we start from the fact that the developer works well, he is sure to have a good income because he will be able to exchange it at the price he wants.
In this condition, the developer must of course be sure of his skills.
You are not willing to say what you want to reward yourself with vs what the developer will get? A developer will want a % of the total coin supply, since they are building it. And since your project will not have income/value on day one, he/she will be working for free. You are not buying your food and paying your rent with this project; you expect a very valuable developer to?
If you believe you can tell them what they are getting in private, and they may stick around, you are wrong. Unless they know how much they are getting and the probability of success, they won't even contact you.