Having lived in and near Riverdale for the past 12 years, I can attest to the fact that it is one of the best neighborhoods in the Bronx. Quiet, clean and with every amenity...as I'm sure you know the prices for houses are determined by the actual demographics, including mean income of the residents in the specific area. It is also close enough to be a painless commute to the city - these things combine to equal a fairly high premium for living expenses including the maintenance for the co-ops in this area.

Usually maintenance charges are designated for coops and common charges are designated for condos.

These amounts and their increases are usually decided by the management company of the building. Often, the more amenities a building has, the more the maintenance charge is. Also the bigger the apartment the more shares a coop has and therefore they may have higher maintenance. One of the things you want to look into are the building's finances are. Is there a mortgage on the property? Is there an assesment for repairs? All this has to be taken into account.

Finally, some portion of one's maintenance is usually tax deductable. Find out from the Realtor you are working with. It's their job to get you this information.