I got into nitro this year and it's been an adventure, deeply satisfying and something I've always wanted to do.
It all depends on your tolerance for troubleshooting - a cheap nitro will teach you all about the hobby, the hard way- the Mr. Miyagi way
A fancy RTR is basically the same as a cheap nitro that's been given a careful once-over and tune by a pro; after that first maintenance cycle wears out, it's much more about the owner's care and maintenance than the model they've chosen.
A fancy model will run more easily out of the box, but will eventually require just as much involvement and maintenance as a cheap one if you want it to last.
I started with the very cheapest model I could find, an HSP Flying Fish, and out of the half-dozen nitros I've acquired, even though I now consider it "the beater", it's my most-driven and most-maintained car. It's the one I'm about to take out after this post!
I think HSP is unfairly maligned as "cheap" given the problems even fancy brands like Arma and Traxxas have shipped with their twice-as-expensive products. They have as solid a design as anyone else, and better parts availability / pricing, as well as lots of common parts between models which is a big plus for fleet maintenance!
My attempts at buying used/project car nitros hoping to save money over a new one have all backfired, I can't recommend it except to complete a collection or acquire rare models.