Not wanting to be discouraging, but investing in speed shops is very risky. Meth labs, sure. But hotrod shops are high-risk, and low return. For every one that makes a solid profit, there are hundreds that either barely hang in there month-to-month or outright fail in less than 5 years. Often the problem is that the owner is a hotrodder, and when he gets some money, he puts it into going faster. Nothing wrong with that, but for outside investors, that isn't going to work.
Your best bet is to do what you know how to do (tuning, fab, engine building, etc) with the bare minimum of capital investment (work out of your garage, rent dyno time, etc) and put away 10% of every sale into the "I Want A Brick Building" fund. If you borrow the money first, your chances of survival are poor, since you will have to pay the loan even in the slow periods, and it will be >20% of your income, not 10%.