Buddy of mine picked up old washers and dryers for free or close enough. Fixed and flipped 'em on eBay marketplace. Made several hundred a week.
The genius is that those appliances are easy to work on and usually have compatible parts. I went over to get a part from him and there were only 2 that fit all American washers.
I used to pick up vacuum cleaners on my paper route. Got stoned at night and cleaned them, maybe added a new belt and bag, perfect. Sold for $20 a pop. (This was in the 90s).
Another friend used to go out with her husband early on trash days and pick up free stuff by the road. Had a garage sale every Saturday, 6-7 hours tops, made $300-$400. "We take our neighbor's trash and sell it back to them!"