Clarify your purpose for purchasing an antique or vintage garment to determine whether or not to make any mends. Keeping a notebook to document any damage and suggested repairs is a good idea for cataloging collectable antique clothing and, for listing details in your ad descriptions. Get organized before starting any mending and do only what is reasonable for you to accomplish - know your sewing limitations and contact a professional for more difficult mends. Give an honest description of any changes you've made to the garment (or accessory) and include photos for providing as much information as possible, to build a trusting relationship with your clientele.