How to Get Rich by Felix Dennis was recommended to me by an adviser that I trust. Since I grew up in my career in high tech at the same time as Mr. Dennis built his fortune I could relate to everything he explained about how his success with the first computer trade pubs and Maxim produced his rise to the ranks of the rich (and somewhat famous). This is a somewhat gritty tale told from a heavy British viewpoint but is nonetheless an accurate description of what's needed to become rich. I didn't say successful or happy, because these have nothing to do with getting rich as you will hear from Felix throughout.
People are always looking to have their cars washed and detailed. You could be a mobile car washer and detailer without having a permanent location. Reach out to people you know or make some flyers and put it in your neighbors' mailboxes. If you want to get serious about it, prop up a one-page website or give out business cards. You can make money quickly doing this.