And people wonder why on-road is dying...look at this mentality.
Jorge, and I don't mean this to come off sounding like an azz...but if you have to ask this question about on-road racing no matter what car and equipment you get, it's going to be better able to perform than you will when you are just starting out.
Focus on getting something to get your feet wet and see if you even like on-road racing. You may hate it and now you have $1,000 in top of the line equipment that you can't even give away. If you do like it, then as your skills get better, upgrade as you go and into the class that suits you best. Maybe 17.5 is too slow for you and you'll want to run mod or perhaps your track has a "spec" division where motor, tires, and ESC are limited. These things will help focus your decisions. Maybe sedan isn't what you want and pan car is more your desire.
Nitro vs. Electric is a personal preference. Generally, electric is more expensive up front while Nitro you have to keep buying fuel. If you have experiance with nitro engines that's a plus, otherwise there is a learning curve to them also that you will have to contend with. If all your tracks are big outdoor tracks then nitro may be more popular in your area whereas if you have a lot of indoor tracks, electric is going to have a bigger following.
On-road racing isn't cheap especially as you get to the higher levels of competition. Maybe money isn't an issue for you but don't get hung up on the "got to have the best to compete" mentality otherwise you'll miss the very important role the driver makes in racing. Getting your car set up to your driving style, whether nitro or electric, makes more of a difference than anything else. I have raced very competitive, high end cars and have turned the controller over to a peer and have them complain how uncontrollable the car was. It wasn't I was a better driver than him, just a different style and my car was perfect for my style but horrible for his.
So a decent, average car will be fine no matter what type, electric or nitro, it is. They'll all get the job done. In novice classes, equipment means very little and even in sportsman classes it's not often the deciding factor.