Aging-in-place is strictly residential although we see articles from time-to-time that takes it to the workplace, social areas, and recreational sites. While those areas need to accessible for everyone who might visit them, work there, or attend them, they cannot be aging-in-place since no one owns or rents that space as their habitat and stays there to eat, sleep, dress, and relax.
To age-in-place means that people live in the home they are in presently - as best they can - for as long as they desire to be in that home. As we typically think of aging-in-place, it applies to older individuals who have found their forever home (the one that they are satisfied living in without any thoughts of moving from it) either because they intentionally sought and chose it for that reason or they just happened to like the home they were in and decided to make a lifetime out of it.
Thus, aging-in-place can take place at many different ages and stages of life. Some people will be born into a family or generational home that their parents and possibly grandparents enjoyed. They will just continue living there, as will their children - at least until they are old enough to make the decision for themselves about remaining in the family home.
At the other end of the spectrum are people in their eighties and nineties who are selecting a new home for themselves (new construction or existing, to be owned or rented).
Then there are all of the ages, abilities, and stories of people who are in a home now that may or may not be their forever home. This does not mean that they shouldn't enjoy all of the safety, accessibility, visitability, comfort, and convenience benefits that available to help them reside in their living space effectively.
This is one of our chief roles as aging-in-place professionals - to help people evaluate their living environment and adapt or modify it for them to achieve the most effective lifestyle possible.
Of course, there are going to be people who choose to remain in their current homes without doing anything to make those homes more suitable for themselves as they grow older in their space. The procrastinate on improvements, decide they don't have the money to invest in modifications or don't want to spend it even if they do have the funds, or simply elect to keep their homes as they are for a variety of other reasons.
We can't serve those who don't want to change what they have now - even if they have lived there for a while and plan on continuing to do so. We need to find the ones that we can help to achieve greater enjoyment of the home they have now or the one they have declared to be the one they are remaining in - regardless of their current age or health situation.
Aging-in-place applies to many stages of life, although our primary focus is on the older people who have consciously identified their present home as the one they will remain in.