There are two types of homes, those built in a factory and those built on site. We call these "manufactured homes" and "stick built homes", respectively. One takes advantage of the efficiencies of modern factories, while the other costs more, is slower to build, and is prone to weather.
Beyond that, there are several types of manufactured homes. The two we'll be talking about are Mobile and Modular. They are BOTH manufactured homes, however, one is built to a national code and the other is built to a local code. Know the difference!
A modular home, being built to the local building code, is indistinguishable from a stick built home. It is still a manufactured home, but is built to the same standard as a stick built home. Sure, there is some discrimination against homes built in a factory, and a modular home is subject to these same stigmas. But, since they are built in a factory, modular homes are usually more efficient and result in less waste and impact on the environment. Since it is built to the same code, the home will appraise the same as a stick built home because according to code, it is identical. Make sure you know the difference between a modular and mobile home, as the first one will hold it's value much better.
Modular homes are created in accordance to the states or even counties building code. This code is often different between states, which is why modular homes typically cost more to build, since they are building on a smaller scale. A manufactured home, more specifically a "mobile" home, is built to the national HUD code, and benefits from being built en masse. What this means is you can put a mobile home on any piece of land, anywhere in the United States. The national HUD code actually supercedes local building codes, so make sure your local home inspector is aware that your home is a manufactured home and is exempt from their particular requirements (for the most part, more on that later).
Manufactured homes are regulated by the Manufactured Housing Construction and Safety Standards which regulates the way they are designed and the way they are built. This national code allows manufactured homes to be placed anywhere in the country. Modular homes on the other hand, must adhere to the local building code, and will be not only inspected in the factory but inspected once placed on site.
Modular homes are built entirely in a factory, and moved to their particular plot of land on a flatbed truck. They do not have a frame underneath, rather, they are placed on a concrete foundation and more typically, a basement. The frames are then returned to the factory for reuse. They are not only built to a certain local code, but are often built to quality control standards that far exceed stick-built housing standards. This makes them a superior quality product in every way. Once on site, they are assembled like a jigsaw puzzle using various chains, ropes, and good ole' elbow grease. It is often impossible to accurately tell a modular home from a stick built home, especially with more exotic varieties such as two, three story modular homes or modular homes that come with garages and porches. Modular homes are not subject to the same stresses and on site conditions that stick built homes are, and are usually assembled in a few hours.
These homes are appriased the same as a stick built home, but will cost you much less. They often will have the same features that modern stick built homes will have, the same decor, etc. Althought they undergo the same strict code inspection, they can be made to any size, and are usually more durable than stick built.
Since they are built to a local code, and since local codes can vary so much, modular homes are a very customizable product. Go with this option if you really like to tweak your options. They are environmentally friendly, and generally more precise.
The reason they are built to a higher standard is so they can be transported for hundreds of miles down a highway. Tell me what stick built home can do that! They are quicker to build and will always cost less with Home Nation than a stick built home.