speedingbullet, excercise of climbing up and down the stairs is a good idea. It’s better than nothing and I’ll keep your mother-in-law mobile longer than she would otherwise be. One of my auntie is 92 and she’s in super shape from stair climbing about 20 times per day. Everybid of excercise counts.
Yes, especially inland, the 2nd story gets hot. It’s good to have an attic fan set on thermostat that draws out the air as it gets warmed up by the sun hitting the roof.
Large 2 bedroom single level homes are best for seniors in wheelchairs.