i am building my first custom computer and for a 15 year old who saved for more than half is life..... this is everything so bare with me
i am building a new computer and i wanted to know, ALL THE requiremetns for a scsi drive
Does my case have to have something special in it?
Do i need special cables, mobo?

You need a mobo with a scsi connector, or a PCI scsi card along with cables, and scsi drives are way more expensive than IDE drives.
My recomendation would be to build the computer with IDE disk drives, you only really need scsi drives for a server.

You need a SCSI controller which can be included on the motherboard or be a PCI card. The controller connects using SCSI cables to the drive. Be aware that there are several different versions of SCSI and you need a controller and a drive that work together, and a SCSI controller with a BIOS in order to be able to boot from the drive. Also check the Linux support for the SCSI card before buying one.

SCSI does provide better performance, but it comes at a rather steep price. A lot of people choose a small and fast SCSI drive for the system (root, swap, and so on) and cheaper IDE drives for storage.

Håkan

so my case doesn't have to be modified right?
and the scsi drives i get for free up to 72 GB my best friends dad's friend somehow always gives him a free computer and anything he wants is in it

No your case will be fine, and if you can get the drives and other hardware at such a good price then I'll have one too