One advantage in buying a more expensive instrument is that you're more likely to be able to get back nearly what you paid for it if you end up having to sell... assuming you looked after it properly, of course!

It's usually better buying second hand rather than new for much the same reason.

Simple rules for buying if you can't find someone experienced enough to help you... and this applies to 'new' and used alike.

Look for obvious signs of damage, excessive wear, or evidence of repairs. The latter is usually obvious from a change in colour of the finish, or a tell-tale line where a new piece of wood has been spliced in.

Check the neck isn't warped by looking carefully along it from both ends - though an experienced eye is more likely to spot problems, you can judge reasonably well by looking at how the end profiles compare.

Unless you understand sound posts, seek advice from one who knows (unless it's obviously rattling around inside!),

Good bows tend to be expensive, so a cheap one is probably false economy. Like Sorcha said, 'balance, straight stick'...

Whilst strings are relatively straightforward to change, they aren't all that cheap. You would normally expect a seller to have re-strung a used instrument prior to offering it for sale.