You are right to think about yard care; that is a problem for me and I have a husband but it was always my job so it is---different---the way he does it. I'm picky, he's not. In my family, we do have extended ties and they are willing to take turns and come help, but that doesn't make me feel to great making work for them.
if I was alone I'd think seriously about a really nice condo where all that stuff is taken care of. Our town also has a neighborhood with stand alone houses that still have contiguous yards that are maintained by the organization rather than you. They are $$$$ though. But one less worry and a lot less time. I think then you could be in for rising maintenance fees so that would be something to consider as well.
One thing that I noticed is that I got slower and slower at getting chores done as MS progressed a little at a time so that something that I did in an hour eventually became an all day job. I was just tired and worn out before the task was done, and that long before I "looked bad" functionally. Sounds like you are noticing that slow down too.
That having been said, prepare for the worst and hope for the best is good advice. Also recognize that your MS pattern will show itself in the next couple of years and you'll learn what kind of ride it will be. I've had MS for 18 years, I was really fine for many years and I wish now my current self could go back in time and tell my newly diagnosed self to relax, cause I worried way too much.
BTW we've owned and sold 5 houses in that time, I was living in house one when dx'd. I'd do it the same, but this house we just finished is accessible and our long term house, and I am grateful. Every decision is made with the idea of ease in mind: landscaping, decks etc.
Now, if only the economy would let us sell the last one..........