One way to make money is by selling the scrap metal from shopping cars. However transporting multiple shopping carts is very difficult. You will surely be caught by the grocery store manager if you are walking away with a giant train of them at midnight. However if I take one at a time they don’t seem to bother me. I’ve done this daily, and stock piling them on the shoulder of the CA-101.
Over the course of a week I had stockpiled about 10. Yesterday I went to the grocery store and got another. When I got to CA-101 I found that they were all gone.