 According to Ivan Reitman (qv) and Harold Ramis (qv) in the DVD  Commentary, in Dan Aykroyd (qv)s original rough draft of the  movie, the story was going to take place in the future and that  there would be teams of Ghostbusters like there are paramedics and  firefighters (thus explaining basing the Ghostbusters HQ in a  firehouse). According to Reitman, such a film would cost "at least  $300 million in 1984 dollars". So Harold Ramis was brought in to  rewrite the script and bring it into modern times.