I believe that walking (anything above 10K steps as tracked by Actifit app) is one of the best exercise you can have, though I do try to supplement it with at least two or three weigh lifting workouts every week.
I agree, but it isn't enough alone at "our age" I think. When our parents were our age, they did physical work more often also, so they would build more daily. Going for a walk is great, but unless really intentional, it isn't going to do enough work for most people. If currently very large, yeah, it is a good way to start getting moving.
but at the age of almost fifty I am afraid that regular running with my 220 lbs of weight might be detrimental for my joints...
I think I am shorter than you (I am only 5´7) but weigh about 200 lbs. I don't run, but I have been using a spinning bike at the gym for low impact training. It has been good.
Yes I am a bit taller at 6' (used to be 6'1' but they now measure me at 6 or 6' 1/2') :) To get 10k steps does take some intention at least here in America :) The physical work equivalent for me is lifting weights in the gym, I have a couple bikes that came with the new place I bought, but when I am there there is so much stuff to do that I don't think I will be able to ride them :) We do have an elliptical that also came with the house, maybe I will use that for low impact as it could be used in shorter time increments...