Well do note that Nitro engines run at 240-280 degrees so it his hand hits one it WILL get burnt pretty good, also the pipes get hot as hell too. The fuel is very poisonous, and volatile too. Personally I wouldn't recommend it unless you plan to be there to supervise it constantly when in use. Also note that tuning can be sometimes tricky so unless you have time to sit down, and watch videos that show how to do things I wouldn't recommend it. Now I have let my nephew run one of my nitro trucks when he was 7 and he had a blast, but that was under close supervision. Also fuel is depending where you live $40+ a gallon, and can be a pain to get if there isn't a hobby shop nearby that stocks it.
Now if you do the Hyper 7 TQ black is a decent buggy, and probably one of the lowest cost nitros I'd recommend (the others I find of good quality the prices jump kinda drastically) http://www3.towerhobbies.com/cgi-bin...&I=LXRUS1&P=ML
Nitro there isn't as much vehicle style choice as electric as it seems they only bother with buggies, truggies, monster trucks and a few onroads for the most part(and before someone corrects me there are others but the majority are those 3 from companies).
Electric you still have to learn things, but its a little more friendly in ways. You have to learn battery care, and most modern RC's pretty much require LiPo's which you have to learn proper maintenance, and safety procedures of. Also electrics have a higher axillary component cost for example batteries are at the low end $24ish a piece, chargers are $40ish a pop, etc. You have to figure out what battery fits in what vehicle as lipos come in so many different sizes its not funny. Motors can hit up to 180 degrees after that they kinds just go poof, plus there is no hot exhaust to hit so its a tad safer
As for electric vehicle recommendations the vehicles costs are all over the place from $100 to over $1k same with the style of vehicles available its all over the place. Exaple they have on-road, buggies, truggies (of all different scales), trail/scale trucks, rock crawlers, Monster Trucks, semi trucks, etc...
(please note with nitro you get what you pay for electric RC's you can cheap out on to an extent)