That 'make two dollars, only forfeit one' isn't the only aspect that needs weighing. To make financial sense, it must not cost the senior too much money in transportation, outlay for approprate clothing, or other hidden costs of most jobs.

Quite a few seniors here cash in on their hobbies: making items for sale, flea marketing, buying auction items to resell, and so on.

Some things I've seen:
Senior couple with home business selling antiques bought at auctions.
Senior who breaks free pallets into kindling, which he sells roadside in five dollar bundles.
Seniors who attend weekly markets to sell baked goods like bread, loaves, cakes, pies, squares. I once calculated roughly, based on cost of ingredients and estimated overhead, one lady was making about four hundred dollars a weekend.
Seniors with large gardens selling fresh produce roadside or at markets, also jams, pickles, preserves.