Question

Hi group,
With all the information that is in cyberspace, I am a little mind boggled.

I am curious about a basic graphic design type of agreement/contract.
How would that be written?

Upon researching, the word "reuse" came up a lot.
How would that be handled?

Upon completion of a job, I usually gave the client a disc. It contained the original art work (i.e. photoshop document, indesign document, etc), a printers folder containing pdf, tiff, etc of high res images/document so they  can have them sent to a printer if need be or their own  printer at home. I usually ask where they will be getting everything printed so I can meet the proper printing specs.
How would that be handled,where I would be able to make more money or do I just give the disc with proper items in each folder?

Anything else I missed?
Unsure if this happens to anyone, but I have come across a few people that want something like a 24" x 36" poster design and about 100 or so prints for almost nothing or a 2" think 8.5" x 11" catalogue designed for about 100 usd

thank you all for your time