First of all what do I mean by a "professional" DJ? By that I mean, be he part time or full time, a professional DJ is one that considers his work as a serious business and will put much time, money and effort into improving that business. On the other hand there are many other people who dabble in the DJ business. You should realize that you may be taking a big chance on your special event. I have have personally seen and heard of many horror stories where special events were ruined because of the DJ's incompetence. If this is not an issue for you, then you may be able to save a few bucks. There are minimal requirements that you should look for in a DJ. First of all he should be responsible; he should "show up" and do what needs to be done. A contract will insure this and will spell out what is required from both you and him. A DJ should be able to play the music that you want at the appropriate time and volume levels - not just the music he likes and happens to collect. Having adequate good equipment to handle the event is important. Attitude is important and also being able to cooperate with your quests and vendors. These are minimum requirements for a decent DJ. However, there are many, many other things that professional DJ's offer that make them worth more.
Is this The Right DJ For Me?
Your first question may be "What is your price?" but the most important question should be "Will you be the right DJ for me?" "These days" every wedding and reception is very unique, so you should closely examine your potential DJ because "these days" every DJ has his unique personality and operates his service differently. You should ask questions to determine if he can make the things happen that you want for your special event.