Is investing in athletes halal?

I previously got a job at UpWork, from **finlete.com**. (a website where fans invest in their athletes and in return will get a share percentage of the athlete's future earnings.) I rejected the offer because I thought that's not halal. Can you guide me? About finlete: https://vimeo.com/731055421 Also, investing in a child's studies so that he could give it back when he start's earning?