I'm Chrissyk's friend who just built a modular in Massachusetts! There are some great aspects to building a modular & there are some pitfall's as well. First, the quality of the home is usually better than stick built homes. They must pass requirements for all fifty states, they're built in a dry enclosed factory, materials aren't left out in the elements....
The costs of a modular can vary dramatically depending on what you are looking for... You can build a small basic modular on your property for as little as 72.00 a foot, our home was completely custom, built from specs we developed and cost in the area of 127.00 a foot...
We found that our builder wasn't able to provide some of the custom options that we were looking for, we did have to subcontract out some of the work ourselves, which meant we had to find the contractor's.... We already had the land, so that wasn't something that we had to rely on.... the prices per square foot doesn't include the land costs.. The builder provided the excavation (including septic) & all services that were required to get the occupancy permit (which we are actually still waiting on)... The problem with any builder is that you have to sit on them & you can't always rely on modular builder's to provide a service that you need (such as paved driveways, walkways, granite work, hardwood flooring, etc....) unlike the previous poster, because we had such a custom job, we ordered the house at the end of August, it was delivered to the property in early December & the custom work wasn't finished until early May... Given the opportunity, I would build another modular... yes, there were some pitfall's, but I think we'd have had them whether the home was modular or stick built on property...
HTH's!