I would obviously pay them if/once the idea took off, but I don't have the capital to do so now.
I own a software services company and I frequently get inquiries from clients who have a great startup idea but are concerned about disclosing the idea to software developers, and subsequently having it stolen. In many cases, these clients ask me to sign an NDA before I can even see the idea and give them some feedback about what it would take to get it done.
Here is what that looks like from my perspective:
1) I don't sign NDA's just to see an 'idea' from a prospective client. This is a hassle and the more experienced, sophisticated clients who actually have money and are serious about their projects rarely ask me to sign an NDA (actually never).
2) An idea, no matter how good, is rarely worth much. It's the execution that is much, much harder. So, protecting your idea should't be a priority - someone else is probably thinking about the same idea right now. Start executing and do it better, faster, and more profitably.
3) Asking for an NDA makes you look like an amateur. Here is why: while you are worried about protecting your great idea, there are other entrepreneurs who have great ideas and they are doing the exact opposite of what you are doing. Instead of hiding the idea, they are pitching it to anyone and everyone they who will listen, hoping to get feedback and improve the idea. Who do you think will succeed first?
4) Finally, it's just not possible to keep your idea secret and have other people collaborate on it. Why fight this battle?
As for getting someone to do the coding without any payment, your only real option is to give someone equity or just have them partner with you for some other reason. In today's market, that is very difficult and even a very good idea with a good team behind it will have trouble doing it.