It sounds stupid, but make sure the kill switch is in the RUN position before you spend money on anything. If it is, then just try to jump the started solenoid with a wrench to see if the starter turns. You’ll know if power is getting to the starter if the wrench sparks and flash welds.
If the starter turns the engine over, then you have it narrowed down to either the kill switch or the solenoid. Both much cheaper than a starter.