Now days second hand vBs are being sold from $55-$80.

Its not That Pricey and definitely worthful as u would have spent $180 for a 3.x and much more for a 4.x.

Just Grab one and stay in peace.
Alternatively PHPBB3 and MyBB are Great Choices. MyBB is a vB Clone.

PS : Ensure that the buyer is reputed and has good image, vB scams are also very common.