http://www.collegemeasures.org/4-year_colleges/institution/berea-college-ky/scorecard/strategic-measures/ says that Berea spends $27,781 per student. With about 1,600 students, that means that it spends about $44-45 million per year (not including room and board, which it does charge students). However, some of the tuition subsidy per student is in the form a $6,000 labor grant in exchange for part time work, so the actual subsidy needed from the endowment may be more like $34-35 million per year. A $1 billion endowment would have to have an investment rate of return of 3.4-3.5% plus inflation to continue covering the tuition subsidy, assuming there were no other things the endowment’s investment income needs to cover.