Do your homework!! Luck is not an option. Research the speaker you are interested in. find out the repair recommendations. For example, (just an example folks). Martin Logan Speakers are excellent speakers. However, how old are the panels? Do they require replacement? Power Supply or crossove updates available from the manufacturer also? Fortunatly, Martin Logan has excellent customer service and still carries most replacement panels for their entire speaker line and really low costs. My Monolith III speakers which I purchased used are basically brand new because I replaced the panels with new ones, sent the crossovers and power supplies to Martin Logan and they repaired and updated them also. For standard speakers, what is the age? are the surrounds in decent condition? What does the manufacturer say about the age of this speaker? After you have done this type of homework, who is selling the speaker? Have you spoken with that person? Why are they selling it? What do they say about the condition? Are they close by? Can you come by to audition them? If I'm selling a piece of equipment, I have absolutely no problem letting a potential buyer come by with their music to demo the equipment first. I don't sell or buy much on line and I am not a member of the amp of the month club. However, people that have dealt with me are happy with their purchase and I never represent equipment as being something that it isn't. Condition or style or cost. Don't cross your fingers and hope for the best. Do your homework first. If the seller is stuffy or won't give you the time of day, move on. There is no such thing as a free lunch. But, there are reputable dealers out their that sell demo or used equipment that will let you take the equipment home for a week or so and let you listen in your own home. That is my number one way of purchasing. Second is Audiogon. I have purchased some equipment on Audiogon and after doing my homework, made the purchase and each piece of equipment arrived in the condition stated, on time and worked great.
Take it slow, do your homework and be careful.
enjoy