RC Monster Jam trucks is a very popular toy. It is operated on battery power. There is no speed specified on truck but one who has played with the RC Monster Jam trucks can fairly assumes that it can move at speed on 12-15 miles per hour.
You can try Hobby Lobby which offers these types of building trucks and more. They are great and have a very large selection which can be very affordable.
You can purchase this on site that sell toys or Hot Wheels specifically. Or by looking at sites such as Amazon.com or Ebay.com.
100 mph
Parts for RC monster trucks are available from many hobby stores and websites. A Main Hobbies is one of the leading websites in RC monster truck parts and is a good place to purchase them.
The most powerful is the Stampede Monster Truck RTR with XL-5, that is a modification which will allow it to go up 40 mph. It costs around 200$ and you should find yourself a big empty parking lot to practice on before you start trying tricks.
If you buy a nitro RC truck, the prices start at $169.99 if you get them at Hobby-eStore. Looking at the prices, some RC trucks are on sale for less than that. http://www.hobby-estore.com/RC-Trucks-s/1323.htm
If you're looking for a fast truck, then the Mattel RC tractor trucks are very good and close to $100.
Remote control cars are suitable for children from four to ten years. I recommend not the big cars, but the smaller ones, because these "monster trucks" can be really dangerous.
Traxxas R/C cars and trucks preferebly nitro 4X4 TRUCKS or the Traxxas nitro sport.
There are on road and off road models of nitro RC trucks. Choose an off road model for dirt roads. More information is available at http://www.rccartalk.com/nitro-rc-cars.html
To get reports on RC trucks, I would check Amazon.com. Amazon has reviews on all sorts of products. Another website is hobbylobby.com. One of those should help.
It is quite fast for the average RC car except for now there are RC cars are available to go 100 MPH