If you catch a sale, you should be able to get a lightweight 5-footer for $650-ish, maybe less. Farm & Fleet in Madison just had theirs on sale at $599. They're cheap, the paint is usually chipping when it arrives at the store from the factory, there are no guard chains, but they work well and are easy/cheap to maintain, and well-supported via their web site. Not exactly geared for frequent intensive use, but then again, there's a guy in the next county who mows for hire at $50-ish an acre. He intentionally uses them, knowing they're cheap, and just resells them to more occasional users after about two years.
At the price, you're talking about a shear-pin model rather than a slip-clutch. I'm sure there are as many opinions about which is "better" as there are members here, but for my money, carrying an extra 3/8" grade 2 bolt in my pocket is no big deal, and I'd rather not have another component to have to service. In almost 50 hours of mowing, I haven't sheared the pin once.
Last weekend I was mowing our 20-acre prairie, and my wife had been hand-raking an adjacent area, and, er, um, set the rake down in the unmowed prairie. I felt a wee nudge as I ran over it, like I'd hit a small animal with the car. Pulled ahead, stopped, set the rockshaft down and inspected the blades and stump-jumper thru the outlet and inlet, and everything was fine. Didn't shear the pin. Julie pulled the rake out of the cut row, and the head had been bent into the most artful 3-dimensional waveform. I'll post a pic later if I remember; it's really breathtaking, the number it did on that rake, and didn't even nick a blade on the mower.