Visit miata.net or autotrader.com – either one of those would be a great resource to locate a miata. See my post below.
Gee, an awful lot of advice here from people who’ve never actually set a tire onto an autocross course. Ignore them.
The people who have actually participated in this sport know what they’re talking about, and you’ll note that they’re encouraging you. There’s a good reason for this.
It’s great that you want to learn how to handle your daily driver at the limits of its capabilities. More drivers should learn how to do this. Heck, there are countries (like Germany) that actually require you to demonstrate DRIVING SKILL (as opposed to knowing, say, how long you can park at a green curb) in order to get a drivers license. By participating in autocross, you’re completing the education that you should have gotten.
Wear and tear? Maybe an issue if you decide to go hard core and compete seriously for the lowest times in your car’s class. Those are the folks who modify their cars so extensively that they end up making them uncomfortable for daily use. You can still have a huge amount of fun with a bone-stock car.
Do it at least once. You won’t regret it. And you’ll find a lot of like-minded folks who can give you some good advice. There’s terrific camaraderie in the SCCA- everyone is there to help each other out. And you might just find a new passion for driving.
Oh, and I autocross my daily driver- a '99 Miata with just under 100,000 miles on the clock. Autocrossing hasn’t wrecked my car or caused me to increase my maintenance budget. But it has taught me a whole lot about driving and, by extension, made me a safer driver. Go for it.
Certainly it’s worth a try. We’ve had lots of Miata drivers post with how much fun it is. No surprise there. But I can think of much better cars than the OP’s ex-rental Mazda 6 with an automatic transmission.
Please, for the sake of all that’s good and decent, at least change your oil weekly, your struts biannually, and shoot graphite into your locks (don’t forget the trunk and glovebox) every six weeks or so. You might also want to lay in a supply of timing thingies. This “hobby” will drastically decrease the life of your timing thingy. Driving, braking, and steering a car at speeds up to 50 miles per hours can drastically increase stress and wear on the working parts.
May God be with you.