Colleges typically want, in addition to a share of parents’ incomes, about 5 percent of the value of their assets, plus 20 to 25 percent of the students’ (Penn settles for just 5 percent of student assets). But there are differences in how colleges define assets. Cornell, Stanford, Columbia and Duke, for example, take into account home equity. Harvard and Princeton do not, and neither does the federal formula. New Yorkers might fare better with one of the elite private colleges, nearly all of which consider regional variations in cost of living. High medical expenses and kids in prep school? A few top schools, like Princeton, discount for both. The federal government and state colleges do not.