Now my kids are learning how to ride a bicycle with training wheels. When they complaint about how hard it is to ride a bike, I remind them that they are lucky that they even have bikes to ride around in. It's so fun biking around the neighborhood. Great exercise and great for the environment.
If you are just beginning to learn how to ride a bike, you can purchase a relatively inexpensive used one on websites such as ebay or craiglist. The three key features you need to keep in mind when you purchase a bicycle are: weight of the bicycle, height and the bicycle seat. Basically, based on what you can afford, you should purchase the lightest weight bicycle, that comes with the appropriate height and a comfortable seat. Features get more technical as you go up in price. Check out the resources section of this website if you are looking to purchase a new bicycle.