Marostica entered the real estate industry in 1977 and is currently a partner in Loveland Commercial, LLC. In 1982, during a downturn in the real estate market, Marostica declared bankruptcy and had judgements from creditors filed against him. He also had tax liens filed against him both in the early 1980s and in the mid-1990s, and has since paid all back taxes. Marostica became financially successful in real estate, and, together with other partners in Loveland Commercial, has donated extensively to local causes, including endowing a chair in the business department of Colorado State University. As a developer, Marostica specialized in commercial real estate, spearheading five Planned Unit Developments in Loveland and Milliken, Colorado.