If you don't have a fuel efficient car, I wouldn't even consider it. If you do, you need to devote a lot of time to it before it becomes at all worth it (100 orders in last 30 days, good ratings, and above 70% order acceptance rate). Once you're there, it's basically as profitable as any other service job, but with the caveat that it's entirely on you and your executive function to work enough (very boring) hours to pay the bills.
Edit: also, wear and tear on your car is gonna be worth more than the job in any job where you use your personal car for 100% of the work. I would consider any of these jobs a temporary measure.
Yep. For this reason, I left my car running when I'd stop, as idling on the hybrid battery was better than needing to cold start the car 50 times a day.