I would set a few hourly rates and pair them with experience level and the amount of hours you are looking to have them at your school.

We all know guard pay can be abyssmal, but is it a green instructor who has never taught before? $15/hour? Is it a veteran instructor who has a long history of success? $25/hour? Anything in between? Anything more?

Just using those numbers, you are looking at $150-$200/week for an 8-hour rehearsal week. That doesn't include games or contests or classes.

Will they have to drive far to get to your school? That should add more cost.

Are you looking for them to be there for every rehearsal? That would prevent them from spending time at other schools and will add more cost.

Unfortunately, there are no good examples of how much to pay since each campus/district has different capabilities. I know a certain 5A one-hs district who pays their guard person $70,000 while there are 6A schools who can barely pay $15,000. It really just depends on what you are capable of handling and how invested you want that person to be.