A school can cover round-trip transportation (no business class), lodging on campus, three meals per day for the prospect and up to three accompanying guests, and three complimentary admissions to a campus athletics event. Schools can also provide a limited amount of money to a student host for entertainment purposes and can pay for the transportation and lodging of up to two accompanying family members.
I do not believe a booster is allowed to cover private flights, but with NIL, who knows what they can get away with these days?