Copywriters use their own writing to develop sales leads. Developing a sales letter can help you generate leads more consistently. If you create a successful sales letter, and learn the rough ratio between letters sent and business received, then you can control your workload. This way you can send out more letters when you have more time to work or send out fewer letters to slow things down when life gets busier.
Sales letters can help you with telemarketing clients, or even gaining new ones. Telemarketing has become a very difficult business recently due to high turnover and new laws. A sales letter can help make your telemarketing clients more effective and possibly reduce turnover. If you can quantify your savings by training employees, you will have many telemarketing companies coming to you because you have shown yourself effective in their difficult market.
Another great area to discover new business is through doctors and dentists. Doctors and dentist are quite often looking for new clients and a well-made sales letter can help increase their referrals.
These were just a few ideas from Dan Kennedy's book. This book is very helpful by revealing new sources of business. Hopefully this article will help you make more money as a copywriter.