By accepting cards, you receive your funds immediately but the individual that you did the work for can pay over time. Even in these more difficult economic times, many people still have credit cards that have unspent values. As a contractor, you may be able to close more jobs just by being able to offer an alternative form of payment.
Also, you can actually process your transactions by using your cellular phone without a need for any other equipment. You dial an 800# and just follow the prompts. The funds are deposited 2nd business day right into your business checking account. Accounts only take a few days to setup so you can start offering credit cards as a from of payment almost instantly.
Many people even look for ads where contractors accept credit cards and call them first. Even if it allows you close only one job a month, the service will more than pay for itself.