Typically, monthly maintenance inludes your property tax (which is the tax deductible portion) heat, hot water, care of the building such as roof maintenance, cleaning of the interior, painting of public spaces, etc. You are responsible for maintaining the interior of your co-op and usually for the electricity you use. Liability insurance is part of your homeowner's policy, and covers the possibility of someone being injured while in your apartment. Therefore it is not related to the price of the place, but the amount of coverage you elect to have. You would have to get a quote from an insurance agent, but it would not be a significant item.