Hi Jacob. Are you already doing the engine repair work currently? have you done any work for an already established shop or done an apprenticeship for an engine repair technician? Assuming you have done those things and are proficient at the repair work it self. You can get a business license and start small. Start from your home garage to keep the expenses low. Keep all advertising online. Use social media and other avenues to get the word out. Get testimonials from your satisfied customers who can vouch for the work thats been done.