"To have a requirement for something": This means you need something.
* Example: "The job has a requirement for a college degree."
"To have a requirement of something": This means you impose a requirement on someone or something else.
* Example: "The company has a requirement of at least 10 years of experience for this position."
Here's another way to think about it:
* "For" implies that the requirement is *necessary for* something else.
* "Of" implies that the requirement is *imposed by* something else.
Ultimately, the best preposition to use will depend on the specific situation and what you want to convey.