Another prefab option is a Practical Assisted Living Structure, 14’x24’, with some models allowing access to the first floor of the primary home.
Forerunners of these updated homes, in the 1970’s, the Australians started building “granny flats,” simple backyard homes for the elderly. Local zoning rules need to be checked out as some states allow these accessory dwellings for a family member and others don’t but may be considering appropriate legislation for them. Some legislation states the cottages need a physician’s verification that the patient needs assistance with at least two daily functions,, e.g. bathing, eating and dressing. The dwellings are removed when no longer needed.
Some long term care plans pay the patient for in home care and they can pay that to anyone, including a family member.