Guys thanks for all of the great responses!
@nitroholic many thanks for taking the time to post a detailed informative post, greatly appreciated for a newbie like me whos looking to purchase a first nitro car.
Now I have a few more questions. I went to have a look at a hyper 7 TQ2. 21 3port from a guy who lives near me. The owner fired it up, and the thing just took off! He tried applying the brakes but it wouldn't have it. Once he fired it up, it looked like it just kept wanting to go forwards on its own.
When stationary, it looked like everything was working ok, sterring, brakes, servos etc. He's offering it at a reasonable price