It's highly unlikely that you will be able to find competent full-stack mobile developers willing to work with you for equity, but if you do, "fair" compensation would be 50% or more of the equity in the Company.

Approaching any developer with just an idea, diminishes your credibility as a potential co-founder. Here's why: If you're non-technical, you must show a "relentless resourcefulness" in moving your idea forward. This means finding the money necessary to get an MVP or even click-able prototype completed to show that while you might not be technical, you have the ability to raise money, and have enough product sense that you can articulate that into a prototype. If you can't raise or spend the relatively small amount of money required to successfully build a prototype, what evidence are you providing that developer that you are going to be able to create value for the business long-term?

Full-stack mobile developers (although this is often quite a misnomer) are one of the most in-demand skill-sets of all Silicon Valley companies. That means that you're competing against established companies that can pay top dollar, and still provide meaningful equity incentives as well as recently funded startups who have further along the road in turning their idea into reality.

I would suggest that you look at hiring contractors (I know of some great mobile dev shops that are reasonable) to build your first version. Expect to go solo at least until you have some form of early prototype. Then, you're in a much better position to attract a technical co-founder.

Happy to talk you through any of this at any point.