There are some questions as to the "legality" of compensation tied to a given school based on NCAA rules.
That's starting to become the focus of some questions surrounding recent public offers made to current and prospective college athletes.
abovethelaw.com
Relevant section from NCAA Q&A sheet as NIL that is prohibited
"NIL compensation contingent upon enrollment at a particular school. For example, institutions should not use NIL arrangements to improperly induce matriculation (e.g., guaranteeing a particular NIL opportunity
upon enrollment)"
Of course structuring a deal such that a kid couldn't hold up his end if he transferred would take care of that