Is Community Based Marketing Trending?

A startups' main goal is to make sure they get a good customer base. Through constant promotion and high costs, they get a decent consumer-base. However, after the initial startup, a company's goal changes and finances need to be readjusted. In order to help with reducing marketing costs, a business owner needs to switch from advertising to new customers to advertising to their former customers, or their "Community Base" as referred in business.