Q: I am interested in buying an 800-square-foot, one-bedroom condo in Manhattan. The asking price is $399,000, and it needs significant renovations. The homeowners’ association fee is $1,941 per month. Two other units in the building are for sale, both with higher asking prices — $620,000 and more — but the association fees are lower, around $1,750 per month. They have been renovated, are on higher floors, and are comparable in size. I don’t understand why these units have lower monthly fees. What goes into calculating them?