Summer courses at Columbia are demanding due to their abbreviated schedule; you should plan on at least three hours of study time for every one hour of class. Keep in mind that introductory courses are at the 1000 level and advanced undergraduate courses are at the 3000 level.
While many 3000 level courses may not list a prerequisite, you may want to have some familiarity with the material from other courses.
When planning an academic program, it is important to honestly assess all outside commitments, such as work, family, and even time to relax.