Get into the crowd first...
If you really want a good insight and you have racing experience, why not offer your services as a pitman for a while. You'll get to learn the ins and outs, the expenses, the most common cars at your track and before you know it someone will offer you a drive and then a 2nd hand car to help you get started.
Dont be fooled, it's at least $2500 to get yourself setup and if you buy the wrong equipment, that skyrockets. From a 1:1 race perspective that's cheap for the performance we get.
Regarding electric or nitro is really a preference. Electric you spend on Electronics and batteries, the chassis are lighter and more nimble and the speed as fast if not faster.
With onroad nitro, it's the smell of racing fuel, the sound, the two speed gears, the pleasure or pain of engine tuning... yep, we're racing!
It's best to get into the crowd as others have mentioned, see what's available second hand and spare the $$ for your own new engines/motors and buy wisely with a mindset of who else can spare you a belt or wheel hub on the day. Dont skimp on servos or radio gear and leave some room for the wife and some shoe shopping otherwise you'll get your ear chewed off!