You don't use a screwdriver for hammering and you don't use a business card for a door hanger. When people are reaching for that business card shoved in the door, it's awkward. You want people to have a positive and organized feeling about your business, not an awkward impression.
Although maintenance professionals use door hangers successfully, there are many professionals who could take advantage of this opportunity. Accountants, hairdressers, restaurants, retailers, health professionals and many other businesses. If you're in a downtown area and you are trying to reach the businesses in that area, door hanger printing is a great way to remind everyone you are doing business.
Door hangers are one of the most inexpensive ways to market your business. So take advantage of this opportunity and promote yourself.