We should be able to easily pay 600k with incentives for wins, attendance, appearances, draft picks, chamionships, bowl games, etc. If he wants more then reduce his assumed contract from 5 to 4 years or negotiate a reduction to the buyout. That's enough time to see a change in trajectory. If he is so confident that he wants big money (with NO div 1 experience) then this shouldn't be a problem.
Also, again, charge each student an athletic tuition fee of $100 each semester. With 25,000 students that is 5 million a year that can be mandated for coaches' pay or other important aspects of the dept . Its a simple solution to the supposed lack of donations.