Dan received a degree in Real Estate Finance from  California State University, Long Beach. He has supervised construction projects since 1979. First, as a superintendent with Century West Development where he had full responsibility for the construction of 10 projects, including three apartments and seven condominiums. In 1983 Dan went to work for Alpha Construction Co. as a project manager where he was responsible for building six projects for the general contractor,  primarily HUD and CRA financed apartment buildings. In 1986 Dan became a licensed general contractor and started contracting and developing on his own. He was President of Rosen/Wiedner Group, a general contracting / development company, that did over $45 million in building from 1988 to 1992. 

In 1994, after the Northridge Earthquake, Dan got involved in rebuilding four severely damaged homes in Bel Air, with the last one being completed in February 2000. During that time, Dan obtained valuable experience working with insurance companies and adjusters, making sure the homeowner was awarded the necessary settlement to rebuild the house, at least to it's previous condition, and sometimes better.

In 1999 Dan was asked by a well-known attorney to be an Expert Witness on a case against a general contractor; since then he has worked on over 50 cases for various attorneys in Southern California. 

In 2000, Dan started Rosen Construction, Inc. and, to date, has completed over 60 projects, ranging from kitchen remodels, custom remodels, water damage repairs and back yard remodels, to the reconstruction of an 11-unit condo.