Best places to buy handmade items:
Not all the items sold on these sites are Handmade. You can make them out based on the reviews or from the product details itself.
Vintage Stuff is likely to come from a thrift store. Go look at one near your home before you start looking for stuff online.
Check the reviews to see if customers were satisfied with the buyer and the item.
Message the Sellers to ask little questions about the products. If the sellers respond in a manner that shows they care about their work, you will feel much safer making a transaction with them.