Bill,
I can't better the advise given by Zax, who is indeed an expert.
All I can say is that, as far as lasers are concerned, there are many pitfalls for the unwary and you are right to observe caution. It is only when you buy from well respected suppliers (such as Ray Scott) that you can relax your guard, but these machines are possibly beyond your price guide.
There are probably more good imports than there are bad imports but we mainly only get to hear about the bad ones so I think you just have to have luck.
Be lucky, my friend.
Tweakie.
CNC is only limited by our imagination.