This really isn't the place to discuss this. You'd be far better suited using a computer hardware dedicated site like
Anandtech.
As Mr. Man suggested, you're also FAR better off going with some sort of NAS set up than you would be with trying to hook all of this up to a single PC.
Having said that, you're going to need to spend quite a bit more than $7500.00 just on drives. With 30 drives, your chance of individual failure within 1 year gets into the probable range. So, you're going to need to be using at least RAID 5.
It's been a while since I've set up a large RAID, so I'm not sure what the maximum number of drives you can stick into a single array is. Going by memory, I know there's a SATA Promise RAID controller that holds 6 drives. If you set that up to RAID 5, then you'd have 1 extra drive for every 5. Which would mean 36 1TB drives to create six 5TB arrays. You'd have to point separate cameras at separate arrays OR set up your program so that every two months it automagically moved on to the next array.
As far as cases go, you're going to want an external cases for each array. There are a number of decent options out there. Make sure that your cases support hot-swap, so that you don't have to take the whole system down every time a drive crashes and burns. Also
A slightly harder point to address is finding a MB with enough PCI-e slots to accommodate 6 RAID controller cards. Good luck with that one.
Two other things to consider --
1) Windows is going to choke all to hell on this much storage. You're going to want some flavor of Unix that runs a file system more robust than NTFS.
2) Does he *really* need 365 days of feeds all on-line simultaneously? It'd probably be dramatically cheaper in terms of maintenance, electrical, and other costs to get a Blu-Ray Burner and just do a regular archive. By my math, you're expecting a usage of 80-ish GB daily (which seems EXTREMELY low for the amount of video you describe). Assuming no errors, that'd be 4 single-sided BD's per day. Those typically cost around $15 each, so you're looking at a cost of $60 in blank disks.
Finally, about 5 years ago, I was involved in a project to put together a storage system for my department. We were dealing with what were then some extremely large files. So, we decided to put together a TB of storage. This ran into the thousands of dollars and created a massive server with numerous RAID arrays all mounted in it. It worked well, and it was definitely necessary for what we were doing. Now, that server is obsolete, and I can get the same amount of storage for $250. Your contact might consider that he's a couple of steps ahead of himself in technology and that if he can wait on this for a few years, he might be able to pick this up for a couple of orders of magnitude less money.