If someone is interested in radio controlled hobbies, they almost always start with a car. Unlike a boat or a plane, cars usually will not be completely destroyed if they fail.
It is very easy to make a basic radio controlled car, but as you do it you will discover that there is a huge amount of knowledge that can be gained. As you gain this knowledge, you can start to use advanced techniques to create cars that are stronger, faster, or more efficient than your previous ones.
You can throw one together in a few minutes, or you can spend months creating an amazing car with superb speed and handling. The amount of effort you put into it is entirely up to you.
If you are just starting with radio controlled hobbies, it is probably wise to just buy a pre-made radio controlled car like this one. Play with it for a couple of days, and then take it apart. Look at the way the motors are connected to the wheels, and look at the general architecture of the car.
After you understand it all, you will have much better luck when you start to build your own. You may even be able to use a few parts, such as the body of the car or the radio equipment. The motors will probably not be as strong as you would like.