I'm guessing that a good rule of thumb is that any job offers on a truck sign or a telephone pole are probably not good career options.
There's a Democratic street soliciting group that keeps putting up illegal postings on light poles in our neighborhood. They go by different names, which is also a big red warning, and post under names like "Work For Progress", Fairshare, and most recently, Grassroots Campaigns. They supposedly hire people to "raise awareness" of issues, but in reality it's just a big scam to make money for some political machine. This is the Facebook site of one of their stupid front firms:
https://www.facebook.com/cofairshare and here's another one:
https://www.facebook.com/pages/Work-...&tab=page_info
If you look up the reviews on glassdoor.com, their business model is something like this:
1. "Hire" anyone who is dumb enough or desperate enough to call. They prey on the unemployed and on young college kids.
2. Give them a clipboard and a sales speech.
3. Send them out to knock on doors, with a requirement that they get some amount of money by the end of the day. That money then funds a sub-minimum wage paycheck for them and makes someone rich.
What's unbelievable to me is that the people posting the reviews on glassdoor.com seem to believe that they're offering real (if terrible) jobs. It's a scam, people. It's not a job. It's a scam.