RC helicopter is not nowadays unusual toy anymore. You can find all kinds of rc helicopters in variety of price ranges.
If you are a beginner and want to start an rc helicopter hobby, it might be difficult. There is variety of power sources and other options you have to know before buying your own first rc helicopter.
Electric power source is most probably the best choice for you if you are a beginner. Electrically powered rc helicopter is really quiet, but still fast enough. You don't have to tune the engine or handle messy fuel. If you are just starting your rc helicopter hobby, it is the best to choose an electric powered rc helicopter and get a fuel powered one later on.
There are also glow engine powered rc helicopters. At first those engines were used in RC airplanes. Glow engines ignition system uses a glow plug instead of a spark plug. A battery is heating up glow plug. When fuel enters the combustion chamber, heated glow ignites it and engine starts up. If you are serious about your rc helicopter hobby, of course you can get a glow engine helicopter right away. It is perfect for realistic flying.
The next challenge after getting an rc helicopter is learning how to fly it. It will be really hard at first so most likely it will crash into the ground at first. It would be good to know how to put it properly together to save yourself some frustration.
The best way to learn how to fly an rc helicopter is to get some experience with an instructor at first. You will still have plenty of time to fly on your own later on when you know how to fly safely. Almost every state and country have an RC airplane clubs. Most of them have experience with RC helicopters too.