First of all there is a huge difference between a condo and a coop. In a condo situation, you own the interior but not the exterior of the home
When you buy into a co-op, you don't own any of the building's real estate. Instead, you own shares or a membership in the cooperative housing corporation. The corporation owns the real estate.
Co-ops can sometimes be tricky, with financial requirements that some older purchasers cannot meet. Selling your co-op could be something of a hassle because the board will be interviewing and scrutinizing your prospective buyers. Buyers will also have to decide whether they can live with the building's rules.
Because co-ops have an unconventional ownership system, it may be harder to get financing to purchase your share. The board also may have rules for down payments, which you'll probably find less flexible than some mortgage lenders. There are a limited amount of mortgage companies that even do co-op mortgages (at least here in NJ).
And, because all the expenses are jointly shared, everyone shares liability. In the rare case that an owner defaults, it will be up to the other owners to cover those expenses.
Condo maintenance fees vary widely depending on many factors, not the least of which is the amenities the development provides (like pool, play area, tenns, club house etc), but usually cover things like maintenance of the common areas, snow removal, lawn maintenance, insurance for the development (you still need your own homeowner insurance), some exterior repairs to the unit.
Co-op montly fees are higher but usually also include all the utilities (water, sewer, electricity/gas, taxes, etc).
If your dad is getting up in years (or even if he isn't) but doesn't want the hassle of mowing, shoveling etc, then a condo is my choice rather than a single family and/or a co-op.