I don't work in real estate, but I've used my Sigma 10-20 f/4-5.6 in house hunting, as well as urban exploration, and it does a very nice job. What's funny about the assertions that the Tamron 10-24 is superior is that I almost bought a Tamron 10-24, but my research turned up comparisons between the Tamron and the Sigma that favored the Sigma. But your mileage may vary. I'm betting that a wide-angle rectilinear lens like the Tamron 10-24, the Sigma 8-16, or the Sigma 10-24 will be great. If I were you, I'd keep an eye out for a deal on a used copy of any of these. If you buy it here on the forum, you can generally count on getting full disclosure of a lens' condition/quality. That's how I got my 10-20 (as well as my K-5 and a number of other lenses). No, you can't have my 10-20.