Join Date: Oct 2009
Location: Just south of sanity
Heart murmurs are indeed quite common in horses, although they're usually found in animals much older than 6.
As far as the pin firing, that's a race track thing. Doesn't necessarily mean he was ever lame or injured, just that they might have done it as a matter of course.
If your vet likes the animal and he isn't also the seller's vet, I'd take his word on not worrying too much about the horse's issues.
The important things are that your husband likes him, and he's an even tempered, sane animal.
Make sure to get the 2 week trial agreement in writing, with the terms and conditions spelled out plainly.