Living alone is not the same as needing no one. The person you care for may have an apartment, an upstairs unit over a shop, or a small place in a building where neighbors come and go. The question is less how many people share the home and more who is close enough to notice when the day starts to drift.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Start with who is near
Make a short list of everyone who could reach the home in a real emergency, and how long each one would take. A neighbor across the hall is a different kind of help than a sibling a long drive away. Write down the building's own helpers too, such as a front desk, a superintendent, or a manager who holds a key.
Ask the building directly whether they would be willing to knock, and whether they know how to reach you. Some will say yes gladly. Some will say they cannot take on that role. Either answer helps you size the support.
Map the stretches that are hard to cover
Take a blank week and mark the times when no one from the family is on the way. Often the gaps are in the early morning, the late afternoon, and the long stretch after dark. Those are the times where support at home matters most, and where the visits should be sized.
Count the stretches, not the total. A visit that covers the morning routine and a later check is a different job than an overnight presence. Decide which job you are hiring first, and only then ask what kind of helper and how long each visit should be.
Fit the visits to a home with one person in it
With one person in the home, a helper is often the only other person in the rooms. Ask how the helper would reach the office if something felt wrong, and what the helper would do if the door was locked or the building would not let them in. Ask who holds the spare key and where it is kept, and whether the building's rules allow a helper to come and go.
Also think about the person's own rhythm. A quiet apartment can feel large in the evening. Some families choose a visit that lands near the time the day usually winds down, so the person you care for is not waiting alone for the next knock.
What to write down before the first visit
Who has a key, and who has agreed to be the first call.
Which stretches of the week have no family member nearby.
What the building allows, and what the building will not do.
How the helper should check in with the office at the start and end of each visit.
Your local area agency on aging is a sensible starting point for questions like these. It can point you to county-level options without making the choice for you. For how evenings tend to look in a home like this, see Evenings and Nights at Home.