Sorry, couldn't resist.
If dialup...you will have a LONG LONG wait. If you are using broadband, know how to verify and burn ISOs, and don't need the manual that comes with Redhat, download. If you want an easier time of it, or you aren't that versed in ISOs, then buy the set. Buying gives you up2date for the first 30 days, which means you will get the entire updates to the version you buy as a baseline.
Personally, I buy because I want to help the cause.