A California real estate investment trust said today that it has bought the 147 rental units at Park Place Apartments, 615 Park St., in downtown Des Moines. The 16-story structure was built in 1986, and since that time 11 of its units have been sold as condominiums. Steadfast Income Inc. REIT of Irving, Calif., said 95 percent of the apartments are leased. “Many of the factors that Forbes (magazine) highlighted in their (2010) review of Des Moines — namely its low unemployment rate, favorable economic outlook, well-educated work force and its dominant positioning as a headquarters city for many major corporations — were key components in our decision to acquire Park Place,” Steadfast CEO and President Rodney Emery said in a news release. Terms of the deal were not disclosed, and a record of the acquisition had not been filed as of this morning. The property was mortgaged for $13.9 million in 2006 by a limited liability company that listed real estate developer Bob Knapp as its manager. Knapp also is listed as a director of Park Place LLC Condominium Association in the records of the Iowa secretary of state.