I did something similar, built an entire app around an undocumented developer api, got a lot of users and then ended up in a good enough position to find out th

I did something similar, built an entire app around an undocumented developer api, got a lot of users and then ended up in a good enough position to find out there was a "hidden" official api for sale and it opened a lot of doors as well even to the same site had gotten it from. For someone as young as that with nothing but time, I'm sure they knew the outcome and it blowing up was probably more than they could ask for.