Hiya. I think that it's wonderful that you're showing initiative and trying to do something of significance while in high school. I am about to say a lot of discouraging things. It is not because I do not want you to succeed. It is because I don't want you to fail catastrophically.
That said: you're in direct competition with my customers for trustworthy Ruby on Rails developers. My customers will spend more money on their projects in the average month than you have spent on everything in your life. It is entirely possible that there exists a Rails developer charging $5 an hour somewhere who can successfully deliver projects. I wouldn't bet on that, but let's hypothetically stipulate that he exists, somewhere.
If he does, after he gets out of therapy for terminal self-esteem issues, he can raise his rates to $80 an hour and be swamped with takers right now. If you say "Hey, I have a tradition of bringing projects in on-time and on-budget and by the way I also speak English and respond to emails within a day", you will be mobbed like Justin Bieber at a Twilight convention. The market is on fire right now. Therefore, if you find a cheap Rails coder, he is broken somehow. It is possible he is broken in an "insufficient business skills" way and just undercharging, but it is far more likely that he is unskilled and unable to deliver projects, and no matter how little you pay him you will just be setting that money afire.
There are non-monetary considerations in working with people. I'm not saying this to discourage you, I'm just trying to send a quick message from reality prior to you being in charge of somebody's livelihood: the non-monetary considerations do not suggest working with you. You are inexperienced at managing projects. You don't know what you want. You have a name picked up for your startup but you don't have nearly sufficient plans ready to start coding it, and you don't appreciate how expensive generating that sort of documentation is. You have wildly unrealistic expectations about what you are about to get into. Good clients have high expected future values after the current project is over: even supposing you and your freelancer successfully build Selfey, which is vanishingly unlikely, the expected value of your custom is zero over the next five years. You also do not know yet the scariest thing about entrepreneurship, which is that even if I gave you a magic Selfey-spitting wand and you brought it into being tomorrow, you would probably still fail because making products is not the primary source of business success in our industry.
My suggestion: without damaging your current academic career, learn to code on the side. Even if you hypothetically eventually end up buying someone's time, you will become a much better customer very rapidly once you start to appreciate more of what you're asking.