Unused car parking space
If you do not have a car but you have a parking spot you could rent it. You will be surprised how much money you can earn from that. There will always be people who need a parking space, so why not renting it if you have the opportunity to do this.
This is also a win-win situation because you will help someone with a garage and protection for their car and besides the money, your neighbors will think that you are home when you are on vacation and it is important, especially in this world full of criminals.
