There are lots of ways to get involved in radio astronomy but they are rarely obvious and do not always offer immediate gratification such as when looking through an optical telescope. Most radio telescope packages involve some construction and software set-up by the user, and that can be time consuming and frustrating especially if there are no clear instructions to guide the amateur. Nonetheless, it is a very rewarding intellectual endeavor to keep you busy to the end of your life. Beginners usually purchase one of the 3 types of radio telescopes, which cost less than $200 each.
via http://www.radio-astronomy.org/node/248