As someone who has been tuning professionally for 20 years and winding down due to age, my advice to you is it's not a business that you think it will be. Many customers are never satisfied, no matter what happens to their vehicle in the future you WILL get a call from them, it's always the tuners fault, and are you prepared to handle things when things go bad and or break while tuning them. About half of the modded vehicles will have mechanical or electrical issues that need to be addresses before they are ready to tune. It's kind of a thankless business. If you do go through with it get a good lawyer to write up a liability waiver and carry a lot of business liability insurance. And also be aware that the EPA is out there looking for shops deleting emissions from vehicles and HP Tuners has eliminated a lot of the ability to do that in their latest software revisions.