It's not so much that you'd get caught as much as there is generally no frequency control for cars. So anyone operating an rc car within 3 miles of you could shoot you down, whereas you'll know if there are planes flying near you. That's the reason for separating the frequencies. The much bigger issue is the style of the radios. It would be a real pain to fly an airplane using a typical trigger type car radio. As a beginner, you'll have enough pains already without having to be saddled with a transmitter that's not made to make flying easier. If you need to save money, search for "transmitter" in the Buy and Sell forum and pick up an older computerized 6 channel with a receiver for around $40. They go even lower if they are non-computer 4 channel units, but you don't get the conveniences of the computer programming.