Use parts from old keyboards or buy a Epic board. Hunt around in your neighborhood junkyard for parts and build your own jet. The best thing about homebuilding is that if you have the room and the imagination, you can create any thing you want. Pop a 17 inch monitor on the hood and wire up the steering wheel for a great Nascar setup. Think about fully enclosing the unit.
Full enclosure allows for a total immersion in the virtual setting.
Build in seating for two so you can share the experience. Get the biggest monitor you can afford. The bigger the screen the more realistic. Don't skimp on sound. Get yourself a powerful subwoofer and mount it under your seat to really feel the impact.