I worked for builders for many years and when I was asked that question, what was usually meant was "how long does it take from contract, to-move-in? That basically depends on demand, the builder, and how many upgrades a person adds. Typically, a builder that is building homes with only the "standard features", in today's market, during low demand, will take about 4 to 6 months from contract to move-in. Remember the builder has to wait about 30 - 45 days to get the plot plan ordered and the permit submitted and approved. But if a buyer is adding upgrades, the builder adds in 2 weeks for the buyer to go to the "design center" to choose options, and adds 2 weeks to install extra features. So now we're looking at 5 - 7 months. But whatever the builder tells you is the build-time, it's a good idea to mentally add 1 month. You wouldn't want to give your 30-day notice to your apartment complex, just to have the builder tell you at the last minute, "we ran into a glitch with the water meter. The city can't install it for another 2 weeks".
I hope this was helpful.