Kyn,
Everyone is giving you great advice.
If you were preparing to graduate from High School, or had just started your Under-graduate education. I would have strongly recommended applying to a College or University which offers a Co-operative Education Program.
The Co-op Program essentially places students in part-time positions in both the private and public sectors with a GUARANTEE that if you successfully complete your degree requirements and Co-op assignments you will be hired full-time upon graduation.
Virtually all Federal Law Enforcement Agencies, including USSS, have Student Trainee or Co-op positions for the GS-1811 Criminal Investigator (Special Agent) position. My office currently has three Co-ops.
In your case, apply, and Good Luck!
.
"When you have eliminated the impossible, whatever remains,
however improbable, must be the truth." Sir Arthur Conan Doyle