Red Line Real Estate is one of several businesses located within 175 Elm Street, and specializes in apartment rentals in Somerville, Cambridge and Arlington. Broker John W. Lowenstein is the owner and primary real estate agent of the company. He also offers cost-free advertising, credit checks and reference checks for landlords. The office has no set hours, and those looking for apartments are encouraged to call at any time and leave a detailed message describing what kind of apartment rental they need. Prospective tenants can also contact Lowenstein by filling out a profile questionnaire on his Web site.