I agree with taking a job with a contractor or local parks and get some guided work experience while you put some money in your pocket and get some movement toward a vehicle.
If you simply can't commit to a summer job, go as a gardener. There is an endless demand for pulling weeds, planting flowers and shaping shrubs. It can have a flexible schedule. All of your tools can fit in a bucket and carry a hoe or shovel (including on a bus). No need for power equipment to get going, just some willingness to work the dirt and learn what is and what is not a weed in the yards you service.
Under that path, you can develop a customer base with a niche service that is in high demand in California that next to no one wants to do. Next season, with more cash and some business experience under your belt, you can turn them into mowing customers and make the commitment to all the costs that entails, or just keep gardening.