Where to find a cheap Solidworks program?

You can’t; the license is through Solidworks! The license is forever but costs $4000 and $1300 a year for updates and maintenance.

If you join an FRC Robotics team you can get the student version for free: https://www.firstinspires.org/robotics/frc

@RocketGuy EXCEPT :

SOLIDWORKS Student Edition Software

With SOLIDWORKS skills, students have a clear advantage in engineering and industrial design job markets. The easy-to-use SOLIDWORKS Student Edition lets students sharpen their skills outside the classroom as they learn to design better products.

SOLIDWORKS Student Edition is available to high school, homeschooled and degree-seeking students (who can confirm enrollment in a degree-granting program or full-time enrollment in a certificate-granting program) or full-time faculty members using the software for personal learning or academic purposes.
Commercial and institutional use is prohibited.
The OP wants to make money (definition of commercial) ! If they find out the OP could be banned forever using Solidworks.

True – If he is learning to use it, that would be educational. Obviously, if he wants to design stuff at home and sell it, then that would be commercial.

There is other 3D CAD software, most of which is a lot cheaper, and some is free. I use Viacad, which is about $50. Some people like SketchUp, which is available online for free.