I'm 17 and I'm looking to take classes for STNA or PCT.

Good Sam where? Yes, 17 is old enough to take the class. Some places might not hire you until you are 18, though, but that is not too far away. Your best bet for economical courses are with an adult school, an ROP (Regional Occupational Center), or a community college. Try to stay away from the proprietary schools, they are just too expensive. You can also find free CNA training at long term care facilities. PCT training is usually on the job in a hospital. The hospital trains people that they have hired for these positions. They might require you to have a CNA certificate in order to be hired.