The are a few eBay sellers that routinely have quality razors and a ton that have "Random" razors at good/great prices but would require you to know a little more about what you are looking at or to be willing/able to do some work on them. In my experience very few razors bought on eBay are actually shave ready (regardless of the listing) but a good vintage can be honed into shape pretty quickly by someone here on the forum. You will need a decent leather strop and probably want a cloth component too. I highly recommend making your own "balsa strops" loaded with some very fine honing compound (like 0.1 micron Iron Oxide or whatever any of the other guys here might recommend), a few strokes on a pasted balsa strop after shaving and before stropping on leather or cloth can keep a good edge going for a long time (again, in my experience). I would advise against adding the stropping paste etc to the leather or cloth strop...keep it on the balsa strop.
I have a BUNCH of vintage razors I set aside with the intention of selling cheap to the new guys. They are straight out of my rotation but may need to be touched up. The only reason I haven't listed them on my website or mentioned them here is I haven't had time to do any work on them. I can promise the price would be right but we might need to have one of the other guys do the touch up work if I can't get to it. (it doesn't take a lot, you can learn to do your own honing but I don't recommend learning to shave and hone at the same time).
As far as what to look for. I would say you should be looking at blades that are in the 5/8" or 9/16" range, the size is easy to use and tends to feel natural in hand. Blades that are smaller than 9/16" can feel less stable in hand and on the face (while you are learning) and blades larger than 5/8" tend to be much more expensive and can be more difficult to maneuver...but if you can find an excellent quality 1" blade at a great price get it, you will thank yourself later. I would avoid razors with a very sharp square toe (tip), this will help to avoid painful accidents. If you do end up with a square tip razor you can lightly blunt the tip by rolling it on the mirror and that will help. Don't be afraid of blades with a "smile" (the edge is slightly upturned at the heel and toe), they are very comfortable shavers. DO be afraid of "Frowns", don't touch a frowning razor. I don't know if it matters much to a new shaver whether the blade you get is an extra hollow blade or a quarter hollow or anything between but I think I would avoid a wedge (wedges can be very different to use and maintain). I always liked the Frame-back razor, they tend to have larger and more creative blade shapes (but some are quite small).
If you are able to inspect closely in person or with good pictures look at the edge (from both sides) to ensure there are no chips or nicks anywhere along the shaving edge AND look at the edge and spine for areas of wear that are significantly different from the other areas. Chips, nicks and uneven spine/edge wear can often be dealt by an experienced honemeister but you don't want your first razor to be a problem child. Many/most vintage razors will show hone wear along the spine and edge, and many will have uneven wear somewhere ...but it shouldn't be substantial. The scales should be intact, no cracks near the pins and no obvious warping. When closed the blade should appear to be centered in the scales. If you are inspecting a razor in person you should be able to observe the blade closing in the scales without touching or scraping the scales. Cleaning and polishing can turn an ugly duckling into a swan so don't be afraid of "ugly" or discolored but do be wary of heavy rust and pitting, particularly along the edge or spine (significant imperfections in these areas can impact the ability to hone a quality edge.
As you gain more experience and try your hand at honing you will learn to spot things that matter and things that you can "fix". I bought tons of trash quality razors and was able to rehab them enough to make them wonderful daily shavers.
