When my father was living here, we only had one major episode, which was on a hardwood floor and on the kitchen linoleum. That was nasty, but pretty easy to clean. I knew a lady whose wall-to-wall carpet was quite stinky.
What changes have you made to your house that were smart or not so smart? What would you change if you suddenly won $50,000 or $100,000 in the lottery?
If you give us specifics there are many experts on this site and many resources online about barrier free homes.
Seriously tho, for us the best choice was linoleum flooring. We actually JUST redid about half of the house we're in for my parents. The linoleum is padded so it's easier on their feet, it was "sheet style" so the floor in both bathrooms and kitchen is just one giant piece, no cracks or spaces between for anything to end up. Easy to clean, and hasn't stained from any um... accidents.
We added ramps to the front and back doors (dad's in a wheelchair, mom can't go outside without her scooter) as well as BRIGHT coloured "curbs" anywhere there is a step down or up. (She is also half blind, and just loves walking off uneven ground... or driving off it.) We also had a door moved to make it easier for them to get into the bathroom at night, and put brighter lighting in all the rooms they are frequently in (150w minimum, glad we could find those in LED lights!)
The only things left that I'd like to have done for them, I'd love to be able to put a cement path out to the "garden" so they could both go play with the plants. They are lifelong gardeners and the only things they can reach right now are the pots I've scattered on the end of the driveway. (8 tomatoes, 2 peppers, cucumbers, assorted dwarf fruit trees, wisteria and jasmine.) And I wish I could make the kitchen big enough for them to "help" me cook, but there's actually no way to do that, expanding it in any direction would cut into either bedrooms or hallways that lead to bedrooms.
The only thing I really regret is the colour choices of most of the rooms. My mom insists that "only" cream will work for any given room, where I wanted actual colours (not dark ones, but visible, lovely colours!) but since it was her doing the remodel, it was her choice. I won out on my bedroom only, mostly because she can't actually come see what colours I picked! lol
When we redid the downstairs bathroom, we replaced the tub with a walk-in shower and a sturdy towel bar as a pseudo grab bar. That has failed, and we'll put in a real one next time. The family room on the first floor can become a bedroom when needed. We were already 50-ish when we remodeled, and did think about little things to make the house safer to age in.
You can purchase GOOD quality ones on amazon and from places like home depot or lowes. We got our first 2 sets in a package, 8 bars for like 40$ from depot (this was 2 years ago tho). Had my brother install them, they're so secure you could hang an elephant off them and they wouldn't even wiggle, lol.
If I could make changes to the house, I'd put in pocket doors wherever I could so that you don't need to widen the frame, still have a real door, but one that's out of the way. Doors make me nuts, now!
This is completely aesthetic, but along the base of walls I found clear contact paper (or some matching the wall paint) and applied it just above the baseboards. Keeps all those wheelchair marks from marring the surface.
If it's within the budget, I'd get central air/heat. As we age, we're much more sensitive to the environment. And air filters. And water filtering at the tap.
I drool over a walk-in bathtub. A wheel-in shower would be great. (Neither will happen in this house .. no room in the bath .. it's TINY.)
Consider lowering all the reach ranges .. front-loading washer, side-by-side fridge. Waist-height access to microwave or other small appliances. Closet rods become harder to reach with arthritis or if limited to wheelchair or scooter.
My best advice: restrict yourself to a wheelchair (if you're not already), for a few days, and see what's inconvenient or downright dangerous. It's an eye-opener.