If you're in the US, this is what I always say... If you wait long enough, you can find anything you want in this country for free. Except medical coverage. FB marketplace I discovered has a plethora of used panniers - old and new. And I have to say that no matter what a FBer is selling it, so much of it is highly underpriced! Don't buy new even at REI - all you're doing is supporting the overpaid CEO's of America (or whatever country they might be from). You have a lot of time to do a lot of research and find gear cheap. For the bike, if you're near a big city, search for bike coops. Thrift stores will save you a lot on clothing and other stuff that you might need. I've worked in bike shops. You can't believe what goes into the garbage. There's a reason why the unhoused who live on their bikes rummage thru the dumpsters! There's also a site called freecycle.org. Don't know where you're planning to tour to, but don't over think it. The great thing about bike touring is...there are no rules. Except that you need a bike.