As always, you get what you pay for. Such accommodations vary from small, compact beach villas with mini kitchens to what would be considered full size apartments suitable for year around living to palatial homes worth millions. Either could describe a unit in a high rise building or an apartment or townhouse within a complex. They could describe a flat or a two or more story unit. Access for handicapped varies - some properties were built before laws mandating such access.
Most properties have a swimming pool or access to one.
Typically the property is cleaned before guest arrival but not during the stay. Ask about access to cloths washers and dryers to ensure a supply of clean towels. Cookware, glasses, plates, flatware are almost always provided. If a microwave, multiple TVs, or a VCR are important to you ask about them. Also ask what size beds are in each room.