To add on to what Ed said here. One other thing I recommend for people to do is keep their trainers, even after they have soloed and moved on to other planes. There are lots of reasons why I recommend this. Even after 12 years of flying I still like to take my trainer out and fly it. It's really fun to take a trainer out and push it through advanced aerobatic maneuvers that you thought weren't possible when you were learning. It's also nice to have a trainer available to take people up for "demo flights". Anyway, the point of my post is that if you have a basic 4 channel radio you can just keep it in the trainer and then you'll always have it ready to fly. Plus, this way you don't have to dedicate a receiver for the computer radio you get down the road for your trainer. So in this situation that 4-channel radio will end up serving you for a very long time.

Ken