Flatland Mfg builds some awesome rails that are perfect for a backyard setup.
For a pressure washer, this snowmaker is designed to work best with pressure washers that have a GPM (Gallons per Minute) flow rating of 2.1 - 3.4 GPM. The washer needs to be at rated for at least 1000 PSI (Pounds per Square Inch) but the exact number doesn't matter too much. If you have a washer with less than 2.1 GPM, replace one of the 4002 nozzles with a plug when you build your snowmaker.
This is a pretty standard electic pressure washer that can crank out a good amount of snow. It lists for $99 but is often on sale. You may need to buy a pressure washer extension hose as well (about $15 at any hardware store or Amazon) if your model comes with a one-piece hose/wand combo as they sometimes do.
1,350 PSI, 1.3 GPM Electric Pressure Washer
Not the most reliable engine, but a good flow rate and a good setup. Don't expect to engine to last forever, but you'll enjoy plenty of snowmaking with this beauty.
Generac 6596 2,800 PSI 2.5 GPM Gas Powered Residential Pressure Washer
This is an awesome pressure washer for snowmaking. Reliable Honda engine, high flow rate (2.8gpm), solid frame.
Power PowerShot 3200 PSI 2.8 GPM Honda Engine Gas Pressure Washer