The first place that I recommend that you check is old dilapidated or burned down city owned homes. This will require permission from the city where you live but these types of homes have copper wire everywhere. Every light switch, bulb and plug, all have copper wire connected to them. Some of these homes may also have copper plumbing that you could also remove and sell as scrap.
Phone company - I barely know anyone with a landline anymore but these types of companies have scrap copper wire galore. Landline phone systems use nothing but copper wire to operate. The wires range from a 2 pair to a 500 pair. The 2 pair wire has 2 copper wires that are wrapped in plastic. They are often buried less than a foot deep and stretch from your house to a little green box. A 500 pair has 500 copper wires and you commonly see this wire going up the pole or coming out of a pipe next to the pole.
The 500 pair is worth big bucks. Two feet of it weighs just under 45 pounds. To get your hands on this copper wire, you will have to get permission from the phone company. They often hire contractors to remove old copper phone wires. You could set up an arrangement with them that will allow you to keep all of the scrap copper wire that you remove.
A few other things that you may be overlooking that have scrap copper wire in them or have parts made of copper in them are extension cords, cable wire, vehicle wires, alternators, speaker wire, copiers, irons, pots, pans, address numbers, air conditioners and box staples. One other great place that you can find scrap copper is at gun ranges.
Always check the current scrap copper prices because some days are actually better to sell your scrap on than others are. You can find this information by checking the stock market or by contacting a scrap metal buyer directly. They follow the market all day and will have the most current prices available.