Buy stuff for cheap and resell on craigslist/ebay. If your good with your hands buy broken cars/motos, and resell. Web Programming/App development. blogging, vlogging, start a e-store. write ebooks or how to ebooks. Online Trading. Sell Avon or herbalife products. Create Aviation t-shirts, start Aviation website. Photography and sell photos online, become a e-writer, etc..

Ho's in different area codes. Good fat burn.

You could volunteer at your local VA hospital. They're always looking for folks to help out in many different ways. If you were a member of the military, you can help your brother and sister veterans. If not, you can learn, first hand, the sacrifices that so many have made so that you can sleep soundly at night. Either way, you'd be doing something good and I guarantee that the experience will enrich your life and make you a better person.

Think about something you are passionate about. Make a product and advertise on a website. Total cost is relatively low depending on the products (keep is small/simple). Also get tax write offs.