If you are planning to use a digital back on the Hasselblad V-system, you could consider the Hasselblad CFV-39 with similar data features and shoot rectangular or square. New digital backs come with a 12 month warranty and most used gear will have wither 6-month or 12-month (depending on the condition) from Hasselblad.
Either way, you will enjoy the 16-bit performance and have deeper blacks and smoother gradations in your B/W shots as compared to the 35mm 12- and 14-bit capture.
When evaluating used equipment, it is a good idea to inspect the back for signs of damage (corners) and the surface of the protective glass plate. It is a big purchase, so it is important to see the back for yourself and shoot with it (just like test driving a used car.) Check the firewire port for solid fit, insert/eject the CF card to confirm no pins are bent, and examine the battery posts for good contacts.
If an online deal is too good to be true, then protect yourself with escrow. Caveat Emptor!
John
Hotwire-Digital
Atlanta DC Miami