One day, you decided you've had enough. Maybe it was breaking half of your bones after falling down a mountain again, or maybe it was another arrow to the knee, (elbow, face, ribs ...) but you are considering retiring. You count all of your coin then sell some dull weapons, dented armor, and silver urns to make a little bit more. There isn't much there.
You remember those days of standing in the rain waiting for a rich merchant to pass by while you dreamed of a little farm of your own. Spending the winter in a two sided tent with no doors, you made plans for raising horses in Cyrodil. Every boss and ring leader promised you great riches, and sometimes it came true. The survivors would drink it all away, buying companionship and snorting skooma. You were paid in rubies, diamonds and exotic furs, and you never put anything aside. Most guilds wouldn't accept you, and the ones that did, would throw you out after a few months. You fought in the military, but you were just a grunt and when the fighting was over, you took your coin and moved on.
You aren't anybody special, but those years of experience have to be good for something, right? If you are really good, you might make it as a teacher. You'd probably have to set up your own training area, and spend a lot of time trying to teach hot-headed youngster how to stay alive. You didn't pay attention when you were their age, and you know most of them won't pay attention to you now.
Skilled in weapons, shield, archery, and armors, you could get a job as city guard, town security force, bouncer in a tavern, or body guard for a retired merchant. You would get a place to sleep and eat, and a bit of pay to buy a drink or two at the local tavern. If you were really good at speechifying you could get a position as herald for a local political figure. Just stand around and repeat what the old guy said, but make it sound really impressive.
You may be too old to sneak very well, knees just don't bend as well as they used to, but you know what to watch for. Maybe find a large shop, and spend your time watching for shop lifters. Might not pay much, and sometimes the rascals will get away, but at least it would be steady work.
Blacksmiths, healers and alchemists will have it fairly easy. As long as you don't mind working for someone else, and doing the same thing all day, every day. Every military and guard station will need thousands of iron swords, horseshoes, pain killers, and hangover cures, but you may find yourself changing jobs as politics change.
Mages have it a little harder, especially in Skyrim. Being too weak to do physical work, you'll have to depend on your spells. Spells that you used a lot as an adventurer, might not have much use for retired life. Candlelight was great for exploration, but unless you want to be a professional floor lamp for the Jarl, there isn't much use for it. At least Flames can be used by cooks, when there is no firewood available. "Hey, heat up this cauldron for me." Raising the dead wouldn't be useful, except for festivals or maybe macabre entertainment at executions.
But to be honest here, you know what you will end up doing, chopping firewood, harvesting crops before the cold sets in or sweeping dirt off the board walks. You'll be the old fart who tells stories of the good old days, but you'll be quiet if they buy you a drink. Maybe Argonians can make some coin as fishermen, or Khajit could go home and babysit kittens. Old orcs can seek good deaths, either in battle or at the bottom of a keg. If you are Breton, you'll probably be assassinated before you get a chance to worry about old age.
Of course, you could do what I did. Run up a huge bounty, and be jailed for the rest of your life. Food, straw mattress, and lots of time to write books teaching younger folk to stay out of trouble.