Valiani makes fine CMCs (I have appreciated my own MatPro since 2007) and I understand the desire to locate a good machine at a good price. But be careful about buying a used machine on the open market, especially if it has to be shipped. A CMC is a very complex piece of equipment and its mechanical assemblies are somewhat delicate. Improper packaging for shipment could result in serious damage.
Aside from the hazard of damage in transit, regardless of brand, it may be difficult to know exactly what you are buying unless you know how to thoroughly evaluate the machine. Your best bet would be to buy a fully reconditioned CMC from Crescent/Valiani directly or from The CMC Doctor. Or, if you decide to buy from a user/owner, I suggest planning to spend the additional cost to have the machine installed and calibrated by Valiani's Chuck Terry or The CMC Doctor. If you are not already familiar with the machine, buy some fundamental training, too. That way, you can make the most of a CMC working it its best.