Random thoughts:
Do lots of "drivers school" type of track events... Get REAL comfortable on a track. Do lots of advanced "drivers schools" that allow open passing... be real comfortable passing in turns, diving for the apex (courtouesly of course), etc. NASA group 4 is good if NASA is in your area.
It's a
big step from "driver school" events to SCCA class racing... i think you really need to know what you are doing before jumping into Spec racing (MHO). Note that "driver school" type events are still wheel-to-wheel, open passing, even timed...
For spec-racing: as I stated above, rent the race car you are thinking about getting and do some events with it, ideally get your racing license in that racing car. Then go buy a car.
Good thing about spec-racing is that you cannot tweak stuff... you have to leave it alone, per the spec's. You have only a few choices to make... bolt-in or weld-in roll cage, etc.
And worry only about disposable items... brake pads, race tires, etc.
The biggest expense is the tow vehicle... you already have that
Race fees are $500-750 per weekend... practice session on Friday... 1 race on Saturday, 1 more practise on Saturday (maybe), and 1 race on Sunday.
Repeat ~10 time in one year. I think you have to complete ~8 events to be competitive. That's a big time committment IHMO. [I only know how it works on the west coast].
Finally, for spec racing (at least on the west coast)... winners get a big trophy and a hand-shake... not even a kiss from a pretty girl, much less any money!