valuation question for a single family residence

[Jeff Zatlin]

I'm interested in buying a single family home as a rental property. Projected rental income would be $850/mo gross. Based on the 2% rule, the purchase price shouldn't exceed $42,500. Using the 50% rule, the price should be $50k. SFR's are offered based on comps, though, and this one is offered at 74k. So I'm trying to understand why the comps would be so high, or perhaps due to the fact that the numbers are pretty low perhaps the rules become a little less functional? Or is this just a no-brainer and I should move on?