Do not confuse them with trailers that you see in a trailer park or those in motion. These are completely different things because trailers have wheels whereas modular buildings just stand on their own on flat ground.
Portable buildings are commonly made of either wood or steel. The materials used are supposed to be durable and made with excellent quality to make sure that the structure is strong enough to stand extreme weather conditions. However, you cannot expect a structure like this to be durable enough to be a home. You may temporarily live in a demountable building but it is not advisable to use this as your house.
One common use of for these buildings is as a temporary office for those who do field work. You can usually find these in army or military camps. Architects and engineers also usually have these in construction sites. Even celebrities and others who work in the entertainment industry use these as make shift dressing rooms or offices when they are on tour or on a shooting location.
Surprisingly, more recently, the number of people using them as homes has grown. It does not take up much space and it's a good temporary dwelling space for those who wish to save up before building a real house. Portable buildings are usually only advisable to use as a house if you live alone or with a couple. These are usually small and there wouldn't be enough space to fit in a family comfortably. It is good to know however, that there are also many manufacturers who have built bigger portable buildings designed to be used as homes. These are usually used by families and individuals who move constantly; basically so they can move their house with them. Others who use these buildings as homes are those with lesser budget. Living in a portable home is good enough especially since most would consider having a house to live in a land to mount their houses on as a blessing by itself.
Another point is that once you already have enough means to build a real house of your own, you can actually resell portable buildings. If it is not good enough anymore, you can easily dispose of it without feeling bad about the money you spent. For sure, the time you spent living in your portable home is worth the amount you spent when you bought it.
More information, please visit : used portable buildings