It would probably be better NOT to buy a cheap juicer. AS Dr. Schulze points out a cheapo will give out pretty quickly. So there really is no real savings in doing that. As was pointed out a centrifugal one doesn't do leafy greens well at all. They just spit out the chewed up leaves with very little juice.
We have a Samson juicer which we have had for about 6 years, it is still going strong, and is very easy to clean. Just take your time and see what will work best for you.