PIX IOS upgrades and registration questions.

[whatshakin]

OK guys, What's the deal with the PIX licensing structure and IOS upgrade process?  Looking on CCO, I found docs that mention needing to register with TAC to get IPsec functionality in your PIX.  Does anyone know whether this registration costs money?  The reason I ask is I am contemplating buying a used PIX off eBay and I want to be sure I can get IPSec functionality without it costing an arm and a leg...the PIX will cost me enough already!   I need to know that if I purchase say a PIX 520/515 with 4.X IOS, what the cost will be to upgrade it to 5.X with IPSec features?  This will be the deciding factor of whether I buy one that has everything already (means waiting until one shows up) for buying one right away and upgrading it to get the features I want.   Thanks a lot.