If you have stairs or steps a ramp prior to needing one is good planning!
A rise of one inch in one foot is easy wheeling, three inches in one foot strenuous for aging arms, four inches in one foot inviting runaway if the chair is controlled by the elderly or lightweight persons.
Stair lifts can keep a loft area viable.
While other denizens of this forum would disagree, change your bulbs above 5' to
LED's while your still safe on a ladder, once changed you *probably* won't need to change them for the rest of your life.
A barrier free entry to a
shower (as in wheelchair accessible!) will keep you socially palatable, stainless grab bars in the
shower will help you rise and settle onto a plastic bench, non skid appliques on the shower floor a lifesaver.
If your hallways and doors are broad, a Hoyer lift can make a fall recoverable by a much smaller person easily.
If you are, or are put, on oxygen therapy an "on demand" regulator will stretch your oxy supply three times as far as a standard regulator. if it turns out you need it get an oxygen concentrator as quickly as possible. A portable unit can go a long ways towards staving off depression.
Vitamin D as well as whole spectrum lighting will help anyone overcome SAD (Seasonal Affective Disorder) a lack of sun and the same damn scenery every day (let alone the mind numbing idiocy of television) on top of creeping infirmity will bring the most resolute character into self doubt.....activity (no matter how limited) is the single best
answer to maintain hope, or at least sanguinity.
While everyone around you will be urging you to retire and not do anything (its the old Union program...nobody moves and nobody gets hurt!) if you join into that program you will regret it in lost muscle tone within days.
Low impact exercise (think stretch bands) will help keep tone, an area devoted to it even better because irritation at setup and break down has many people skipping even basic maintenance.
Install wireless doorbells in the upstairs downstairs, shop, and any outbuilding / garden area
( I used these)
https://www.google.com/aclk?sa=L&ai=DChcSEwiaqbrx5fvsAhUJicgKHYvnAc4YABB7GgJxdQ&sig=AOD64_38KEu-9rIxCS0LoojLTBm9hebFYQ&ctype=5&q=&ved=0ahUKEwil37Px5fvsAhWFiK0KHf1NCe4QwzwI7gM&adurl=
Put buttons at front and rear doors one next to the shower, one next to the phone, and get a couple to carry in your pockets. You can program them for different ring tones for the front door, rear door, a different tone for "the phone is for you" and a different tone for "Panic! come help me!!"
If a loved one lives next door you can get boosters so the "Panic! come help me!" will ring at their house too.
A "help I've fallen and can't reach my beer" system is good too, but....has a monthly cost, and a visit from emergency services,
Too many false alarms will result in a case worker herding you into a rest home....
On the monetary scene:
Establish "pay on death" if you have independent accounts.
If any real property is in play put it in an irrevocable trust with a trusted third party as administrator, it has potential to keep your end of life medical bills from swallowing everything.