The main advice I have is that the cost of preparing a home for long-term living is much cheaper than assisted living - even if it means some moderately expensive renovations like Mart’s excellent idea to make an entire bathroom wet. That is exactly what we have planned for our master bath. A zero-entry shower tremendously reduces fall risks, and a wet bath can accommodate shower chairs and a wheelchair. Toileting and showering are the number one reasons people move out of their homes and into skilled care.
I would go ahead and put grab rails in the toilet. After watching my parents and in-laws age-at-home, those rails were inevitable. We also installed bidet toilet seats, which were extremely convenient and not expensive at all.
We purchased carts that helped them move items from their cars to the front door or to the kitchen if coming in from the car. In the garage, we installed hanging tennis balls so they would know where to stop the cars since depth perception became an issue. Get heat tolerant tops so the carts can also be used to move plates, pots, and serve ware across the room. The warning here is that those carts should never be used like walkers.
I also put Amazon Alexa’s in every key room and set them up for verbal dialing, especially for emergencies. They also became helpful for making grocery lists and reminders. My mother had an emergency call button, but the thing kept going off when she bent over, thinking she had fallen.
Getting rid of the extra clothing and stuff is essential, and go ahead and arrange everything how YOU want it. It can be extremely confusing to move things around once cognitive issues start creeping in.
Eventually you will want to consider sprinklers or a sprinkler system that will water your yard and gardens without having to go outdoors.
Change out twist door handles to French lever-style doors. As you replace faucets, likewise install ones that lift rather than twist. Make sure that all faucets have CLEARLY marked hot and cold symbols (blue and red).
Go light as you replace items over the next several years. You don’t realize how the weight of dinnerware, power tools, garden pots, and the like can become such a hassle once arthritis and mobility are issues.
Start staking out where you want motion and solar night lights. My dad installed motion night lights that illuminated whenever one of them got out of bed, entered the bathroom, or the kitchen.
I don’t know if your parents have dogs, but we put trackers on the dogs in case they got out so they wouldn’t chase them and we put soft bells on the dogs, so they would be aware of the dogs’ presence, so less likely to trip over them.
I agree with Lincolnshire about falling. Start now to keep your mobility up by practicing daily to stand up from a chair using no hands, and practice getting off the floor.
Hope this helps.