Many marketing agencies offer lead generation services for business that don't wish to develop their own systems. These agencies will often have a network of companies and websites that it uses to promote its client businesses. When a visitor expresses interest in one of the agency's clients, the agency passes that lead back to the client. Often agencies will promote their clients through a directory or list of providers, and when a visitor requests a quote for a specific service, the agency alerts the appropriate client.
Sales leads are generated on the basis of demographic criteria such as FICO score (United States), income, age, household income, psychographic, etc. These leads are resold to multiple advertisers. Sales leads are typically followed up through phone calls by the sales force. Sales leads are commonly found in the mortgage, insurance and finance industries.