Short answer: Yes.
Slightly longer answer: Websites are essential to a web presence nowadays. A website gives a business legitimacy and is a place where potential clients can get to see whatever carefully crafted image you want to present to them.
That said, you need to be careful in putting the site together. If your site looks sloppy and amateurish, people are bound to make that assumption about you. A well-presented and constructed website can mean the difference between losing clients at your door, and bringing them through.