Ok Scrap, this is gonna be kinda long. Most people will tell me what the PSI of the machine is, but hardly ever refer to the g.p.m. as you did. GPM is gallons per minute as you already know. You can have all the pressure in the world, but if you don't have the gallons per minute, it doesn't do you any good. I snapped a few pics of my cold water machine this morning for you to show you what it looks like. This is a machine that is designed for day in and day out use. It has a Honda V-Twin electric start motor on it. The pump on it is a general pump, www.generalpump.com and the unloader(The green spring) is also a general. Ok, there are three types of pressure washer drives. Gear, direct and belt driven. Most pressure washers that you can buy for use just at home are direct drive. That means that the pump is bolted straight onto the motor itself. This is the worst of the three drives from a contractor stand point, but for use at home from time to time , it will do fine. The best drive is a belt drive because a combustion engine has micro jerks in it and the belt doesn't allow the jerks to transfer to the pump. You can see in one of the pic the big red vented guard covering the 3 belts coming off the engine and going to the pump. I wouldn't suggest any other kind of motor except Honda. They are all I have ever used and simply have never wore one out or blown one up. The cold water machine before this one was a 11 horse that I ran for ten seasons. I wished I had an hour meter on it just out of curiosity. Lowes here sells a little pressure washer that has a 5.5 horse, Comet brand direct pump and removeable tips for around six hundred dollars. A good washer for you should be AT LEAST 3 gpm and AT LEAST 2500 PSI. My cold water runs at about 3850 PSI and 4.8 GPM. As you start approaching 5 GPM, most houses can't put out that much water and the pump starts sucking water out of the hose instead of just letting it flow through. Make sure to get a steel wand and gun with removeable tips. Those plastic adjustable types are cheap pieces of crap and won't last anytime. Last but not least, make sure the machine has an injector. This is used pull chemicals in the hose and mix them automatically. Those are what those kerosene jugs are for on my trailer.
You can see my injector attached to the hose hookup. It is the clear tube and I simply put it into my jug of chemicals. Hard to beat bleach on vinyl, but thats it. No bleach on metal, gutter, soffit, decks, roofs. I buy cleaner that I use on roofs, gutters, concrete and decks from a local guy here by the 55 gallon drum. www.mightyboss.com. I hope this helps. If you have anymore questions, drop me a line. FATBOY