Honestly, you're not very likely to find one online. Locally you might be much better off, depending a bit on if you live in a large city. I'd honestly just try Facebook first. Ask friends and family. I wouldn't mention any payment, at least at first - most people who want money for things like that won't be the best mentors you could get. Finally, consider if there are any groups for developers around you. Women in development, women in Python, Swift developer groups - stuff like that. Not only might that be a help in finding a mentor, but they might actually be better than a mentor in many ways, especially in sharing experiences, since many is often better than one. Good luck!