buying used HD io and hd nativa Thunderbolt card

[eduy]

hello,

I never purchased Avid hardware before, but im interested in buying HD io 16x16 Analog this year and hd Thunderbolt native card.

I saw many used sold separetly in eBay, just the units, but my questions are:

1) Will i be able to use the units without registering them to my name or the previous owners have to transfer ownerships if they are already registered? what problems would i have or what would i miss if those units are already registered by another persona? will it work and i only lose warranty?
2) what happends if previous owner dosnt want to transfer ownership after i parchase used from him?
3) transfer is free?
4) they are bonded to a pro tools account or i can buy my own pro tools License after when i want?
5) is the Problem only with pro tools software account or with hardware too?

my main doubts are, what are the difference from a new hd io and card, to used hd io and used card.. because price from used is like 50%..

if someone can explain i appreciate it.thanks a lot