About paying for distros, which you seem to be a bit confused about. Linux the kernel (core of the OS) and most of the basic tools are open source, which means that you are free to do whatever you want with it for personal use. It also means that all you need is the source code to use them, which is always available for free. The vast majority of other applications available for Linux are also open source, but not all of them.
Red Hat, Mandrake, and Suse are all businesses, and of course they are going to encourage you to give them your money. To this end they do things like offer service deals, bonus downloads, and their own proprietary add-ons to their versions of Linux. But you're free to ignore their pleas for money as they all offer their distributions for free as well.
Other distros like Debian and Gentoo are not run by corporations, but have been developed by groups of volunteers. The most they will ask you for are donations to help the cause.
So you needn't worry about paying for anything. But you might consider giving them some support if you find that some version of Linux is of benefit to you.
One final bit of advice. The various distros really do have their own characters. If you should happen to find yourself frustrated and put out by the one you choose first off, I'd suggest trying out another before giving up. I switched from Mandrake to Debian, for example, because while Mandrake was much easier to set up, it was much more frustrating to maintain and upgrade. Debian was hard to set up, but much easier to work with once I had it going.
Here's a good rundown of the various major distributions: