Build a back end. It costs less and takes less time to sell something new to the customers you already have. If you're not sure what this might be, try asking your customers what else you can do for them. An acupuncturist, for example, could also sell nutritional products. A dry cleaner could offer film developing.
Consultants often find that clients have many other needs, once they begin working on a project.
If a client needs something that you can't provide yourself, consider subcontracting the business to someone else, or collecting a fee for making a referral. If you find yourself struggling to sell to people who often can't afford you, try looking for another market that can pay what you need to charge. Change your pricing. Any marketing expert will tell you that pricing is magic. When you lower prices, sales go up.