Welcome to the Guild, Lab205!
While we certainly prefer participants to lurkers, everybody is welcome here.
There are plenty of great applications for mapping that fall under the FREE designation: GIMP, Inkscape, and countless other tools. There are tutorials for using those apps in this forum, so you don't have to feel you can't afford the tools necessary to craete masterpieces. Many of the best maps on this site use those FREE applications.
Any maps that use with a CC license attached is free for you to download and use in your personal games, while some versions of that license allow you to post elsewhere, you do need to mention its creator and the source of that map. Note: some maps have other licenses including All Rights Reserved, which do not allow you to download and use, as they are generally for paid-for maps used in actual publications.
Enjoy your stay, explore the site, and definitely download one of those free apps, GIMP is a good place to start as their are plenty of excellent tutorials to get you towards making your own masterpieces. And post a map soon, the best way to learn is through the comments, critiques and suggestions on what to do next.
Again, welcome to the Guild!