Not sure if someone else has covered this, but my opinion is don't buy anything on Reverb that doesn't allow refunds, i.e. that is sold 'As Is Described.' Here's why: the way 'As Is Described' works is if they sell you something that does not 100% bear up to what is actually contained in the ad, then you have recourse and can get your money back if it gets to you in any condition other than that which was 'described' in the ad.
But if there's something wrong that wasn't mentioned in the ad - even if you asked in a PM 'does the neck have any issues' - that doesn't count. And I have a feeling that a dishonest person would know this. IMHO, there is no reason for anyone to sell an item on Reverb 'As Is Described.' Either you stand behind your product or you don't.
Having said all of this, you can do pretty well on Reverb if you're a tough negotiator. Keep in mind, Reverb just increased their commission to 5%. So sellers inflate their prices by at least that much, and sometimes by a lot more.
For small sellers, sending someone a bad product means they give you a bad review and tank your rating... which is easy to do since most individual sellers have a perfect five stars. But yeah, not much recourse for the victim of the bad product
I've usually gone with selling 'as is', but I pretty much only buy and sell pedals on there, so it's easy to keep everyone happy.