The young guy at my door said the infamous words: "The offer is only good for today." And he wanted payment in cash. That put me on alert. He was selling driveway resurfacing. Said he had enough asphalt left to do only one job, and he'd give me a good deal. I told him no.

There are some rules of thumb in this experience, when it comes to home maintenance:

1. Beware those who come to the door offering services. Take their card, yes, and ask for a price if you're interested, but don't agree to any work either verbally or in writing.

2. If the work is something you're truly interested in having done, do it a different way. Start by getting references from friends. Ask whether they're happy with the job that was done, and whether any issues were taken care of promptly. Get legitimate bids from people you call, not those who show up at the door.

3. Call the local Better Business Bureau to check on any complaints.

4. If your job involves skilled labor, just as with electrical or plumbing, ask for a copy of the license and verify it with the state agency.

5. Ask for a copy of the insurance certificate and verify it with the company.

6. Don't sign a contract you don't understand. Have a trusted adviser go over it with you. Refuse to be rushed.

7. Beware giving a large down payment. If a supplier will be involved, call them and ask for a reference.

8. Certain types of work require a permit. Verify with your local authorities.

Not all those who come to your door are scammers, but the odds are increased for any type of business relationship that you don't initiate yourself.