Many of the D&D 3rd edition resources are available freely online under the OGL license. There's a great resource at
d20srd.org. However, if you're just getting into 3rd edition right now I would recommend looking into
Pathfinder instead. It's very similar to 3rd edition D&D (much closer than 4th or 5th edition D&D) and still has active support from publishers and a larger playerbase. It also has a much lower cost overhead. This is because in 3rd edition almost everything outside of the player's handbook requires you to pay for it, but in Pathfinder they've extended the free licensing to cover almost everything, so you can find any class, feat, or spell in legal online resources with a quick google search.