I agree with Drew and Ed. You can pick up a real nice Cambo or Calumet lightweight 4x5 monorail for $200.00 or less. If you don't mind if the camera is old I have seen monorails go for as low as $50.00 on Ebay.
Many times you can get a great deal on a 4x5 monorail with a 210mm lens, film holders, etc. included.