I've made many a steal on eBay, where vintage clothing is concerned.
A few pointers:
1) Many sellers have no clue what decade their clothes actually come from and mislabel them
2) Some sellers just put "vintage" on the title when the item is anything but, the better to sell it
3) Often, a vintage dress will require the proper undergarments (corset, crinoline, &c.) in order for the dress to fit right (think of all those clothes with a 25" waist, for example)
4) Frequently, you'll need to perform minor fixes and/or alterations to the dress before it's wearable (seams, hems, stains, &c.)
5) Sometimes, there's a smell factor. This is easily fixed, if the item is made of a washable fabric: dip it into a big bowl filled with vinegar and water for about 10 minutes, then wash gently by hand in Woolite (thank you, Carson Kressley)
6) Measurements are tricky, but most sellers recommend that you take a garment that fits you well, lay it flat on a table and take measurements from armpit to armpit, and waist. That way a garment whose flat fabric measurements match your garment are likeliest to fit
7) Most clothing items are non-returnable, so caveat emptor.
The best and securest way to pay for your items is via PayPal. An account is simple to set up and you can pay either with your credit card or a bank account. I've been using them for almost 10 years and have never had any problems. Just remember NEVER to click on any emails that purport to be PayPal — they're usually not. You can see all real PayPal correspondence to you on their site. Same goes for eBay emails.
One last tip: SNIPE. Various sites, such as AuctionSniper will bid on your behalf seconds before an auction closes — that way you don't have to virtually stalk the item yourself, and you're more likely to snatch an item and at a better price.
But, enough of my prattle. Here are a few things I found last night. Some close as early as today, so get bidding, if something strikes your fancy.
Late 50s/Early 1960s