A condominium or co-op owner has to pay not only a monthly mortgage but also the maintenance fee. In an expensive unit, this can run into thousands of dollars over the course of a year. Granted, some of that is probably tax deductible, and the money goes for maintenance and other common costs. Nevertheless, some people see the combination mortgage/maintenance fee as similar to paying double rent. Thus, the older couple who wants to trade their large house for a small co-op might find the various costs prohibitively expensive when they are all added up.
Because many condominium and co-op buildings are older, converted apartment houses, chances are that maintenance and repair costs will be quite high. For the condominium owner, this means higher repair costs within his or her own unit. For the co-op owner, this means higher monthly fees to pay for repairs throughout the building.