A lot of people shy away but I don't.
All my mics came from ebay; No exception.
The odd one was new, but most were used.
Bottom line is, if the seller describes it as working or whatever and it arrives in any other condition than described, then you're entitled to a refund EVEN if they say no returns.
I'll admit, it's preferable to test a mic before buying, but i figure ebay has that covered because you're not going on someones word, you're going on their legally binding written word.
Just read the description carefully. That's the 'homework' on ebay.
I've only ever had one transaction that went wrong and the seller was difficult, but I handled it properly.
I stayed polite, informed him that I'd be opening a case with ebay when it was appropriate etc. I got a refund ASAP once it was opened.