Modular homes in Montgomery County are very rare. I would say there's a general bias against modular homes with buyers. There's a general perception that the quality is not up to par with site-built homes. In reality, however, the construction can be superior in many regards. Since these are transported, the framing must be sturdier given that it's shipped from a factory. Modular home builders also have the opportunity to do a much better job of quality control since the homes go down a factory line with very skilled employees that do the same thing (plumbing, drywall, etc) over and over again.
I've always expected that we would see more and more modular builders given the big advantages they have. However, the economics just haven't been there. To be cost effective, the 'factory' has to be within so many miles of the home sites. If it's too far, all economic advantages evaporate with increased shipping costs. I believe that a couple of our big local builders - NV, Pulte and maybe others - are doing more to assemble house sections in a factory and delivering them to the building site.
OK, so what do you do?
#1. Check out the builder. You should even visit the factory if possible. Get references from previous homeowners that have been in their home 5 years. What has their experience been?
#2. For re-sale, be aware that some buyers may have a bias against modular homes. So, when you buy, I would negotiate lower than if it were a site-built home. Having said that, given that modular homes are so rare here, very few buyers or agents are familiar with this type of home. When it's time to sell, they may not even know its modular.
Good luck - I hope that helps.