First come the billboards. As you head north, away from downtown Denver, they flip by like flash cards, advertising houses by Lennar, KB Home and Richmond American, from the $100s, the $170s, the low $300s. What they don't tell you is that should you wander into one of the new subdivisions popping up from the prairie, you're likely to be offered tens of thousands of dollars in incentives to buy, and to buy now. At a recent conference of Colorado builders and real estate agents, one speaker counseled salespeople to stop acting so desperate. "It sends the signal that the market is bad," he said, "and to wait for the bottom."