As far as I know, there are no retirement communities dedicated to Parkinson's specifically, although some may offer special support to those suffering from this illness. My mother had Parkinson's
If the senior you are looking for is in bad shape and unable to care for him or herself, however, then a skilled nursing facility is the proper place for them, or at home with a caregiver.
As always, you want a place that is clean, that has enough staff per residents and does not smell when you walk in. When you look at communities for your parent, do ask what they have to offer for someone who is suffering from Parkinson's and use their answer as a criterion in helping your parent select a new home.
and she lived out her entire life in a retirement community. At the end she hired her own caregiver, but she was able to function.