If you’re hiring a contractor to make improvements on your home, be alert! Home improvement scams are more common than you may think, and they can cost you a lot.

Here are 8 ways to spot a home improvement scam:

1. The contractor insists on being paid up front

Be wary of any contractor demanding that you pay most of the fee up front. This is likely a scammer who is trying to cover their bases in case of shoddy work or even a no-show.

2. The contractor refuses to supply references

Never hire a contractor without speaking to someone who’s used their services. If a contractor is in the middle of another job, ask if you can check out their work yourself. If a contractor refuses to furnish names and contact information of previous clients, move on to other options.

3. There’s negative information about them on the Better Business Bureau (BBB) site

Before hiring any small business you’ve never used before, check them out on the BBB website. You’ll be able to read reviews and ratings and see if complaints have been filed against the company.

4. The contractor demands payment in cash

Cash leaves no trail and makes it easy for scammers to walk away without doing much — or any — work.

5. The contractor will work for an insanely low price

If you’re offered a bid that is a lot lower than the going price, ask questions.  There’s a good chance you’re dealing with someone who will cut all corners. If you only get evasive answers, look elsewhere.

6. They show up at your door … uninvited

Don’t fall for every contractor knocking on your door and claiming to have done recent work in your neighborhood. Your uninvited visitor is likely a scammer who will do sloppy work, leave the job half-finished or disappear with your money. If the contractor does seem legit, look them up on the BBB site and ask for references.

7. The contractor refuses to put anything in writing

Never hire anyone to do work on your home without a written contract. Include as many details as possible in the contract, like payment terms, a definitive date for the work’s start and completion, warranty information and a clear description of the job.

8. They try to avoid permits

A contractor who tries to convince you there’s no need to pull permits is one who wants to avoid the authorities. You’re likely dealing with an unlicensed worker or one who will cut corners.