It is true that most of the world's urban areas are becoming larger, with megacities like Delhi, Jakarta, Shanghai, Beijing and Manila adding more than five million people in the last decade and most other urban areas are growing, but not as fast.
1 With professional installation, a central vacuum system can cost $800-$4,000, but averages about $1,200-$2,000 for new home construction (or as part of a remodeling project where the walls are already torn open) and $1,500-$2,500 for retrofitting an existing house.
Plan on spending at least $350 to $400 on the clutch, driven pulley, jack shaft, bearings, gears, and chain. See the first link below. A 12 HP Briggs & Stratton horizontal shaft motor is going to cost you at least $500. About $750 for a 12 HP Kohler or Honda engine. See the second link. An alternative may be to salvage an old motorcycle.