You can accept up to $10k PER YEAR, and that is after you have paid your expenses. Can't think of many 18 year olds in recent memory (who are remotely interested in college) who are even close to that threshold...
12.1.2.4.2
Exception for Prize Money—Tennis.
12.1.2.4.2.1
Prior to Full-Time Collegiate Enrollment.
In tennis, prior to full-time collegiate enrollment, an individual may accept up to $10,000 per calendar year in prize money based on his or her place finish or performance in athletics events. Such prize money may be provided only by the sponsor of an event in which the individual participates. Once the individual has accepted $10,000 in prize money in a particular year, he or she may receive additional prize money on a per-event basis, provided such prize money does not exceed the individual’s actual and necessary expenses for participation in the event. The calculation of actual and necessary expenses shall not include the expenses or fees of anyone other than the individual (e.g., coach’s fees or expenses, parent’s expenses).
(Adopted: 4/26/12, Revised: 1/19/13 effective 8/1/13)
