I once spent several weeks during the run-up to Christmas stranded on the couch after a cycling accident. With nothing better to do than surf the Internet I did all my gift shopping online and bought a winter coat. I looked at many examples, new and vintage, from many different sources and I passed up a number of brand new mid-range coats to buy this one. I've not regretted it for a moment. They really don't make 'em like this anymore.
Buying vintage online can be a gamble when you can't be sure what you're looking at. Used garments rarely declare their quality in amateur photos taken by independent dealers. It's far harder to assess fit when all you have are a vendor's measurements. How can you tell how fabric feels from an image on a screen? All you can do is use your imagination and trust your experience.