Budget is important here like everyone has mentioned.
A Heng Long (for example) brand is an inexpensive RTR that looks like a tank and will be the bottom dollar around 150 to 200 and is more toy like in operation and control. It offers a radio and battery in the box.
Taigen is a much more refined RTR, runs about twice what the HL does and will operate and sound more closer to a hobby grade vehicle and does come with the radio.
IF you want to build your own, a Tamiya can set you back starting at about 600... then you need to add the radio, batteries, charger and such. Many hours involved but many different choices to make along the way of assembling it PLUS painting too.
If I knew nothing about these, I would start at the bottom and then decide how expensive you want to go.
Jeff