Buying a violin isn't like purchasing consumer goods. This is because, with the exception of many beginner-level instruments, violins will often improve with age (and high-end instruments can even increase in value). Therefore, you should approach your purchase as if you're buying a collectable item that won't go out of fashion.
Remember that 'second hand' doesn’t mean 'second best'! Many of the finest violins on the market are old or 'vintage’ instruments, and age (or previous owners!) is generally a FAR less important consideration than things like sound quality, maker, condition, and budget.