My wife, home alone, opened the door to a door-to-door salesman.

[LogDog75]

34. One way to stop them in their tracks is to ask for the city license/permit for sales

Where I live, you have to have a license to do door-to-door sales. I've had people come to my door trying to sell something and I ask to see their license. Some have them and other don't but I tell them I'm not interested.

If you do express interest in buying contracting services, check with your state contractor licensing board for the following:
1. The classification of the business
2. Current contractor's license
3. Current bond with an insurance company
4. Current Workman's Compensation insurance

I was the president of our small 1-unit HOA and when I went out for bids I ask for their contractor license number so I could check them out.

Also, lowest bidder or highest bidder doesn't mean you get you're money's worth so weight each contractor carefully to ensure you're not overspending.