Trailers usually fall apart and depreciated in value. If it just going to be you living there, why not look into a "tiny house". There are many website and places to find them. "Tiny Tumbleweed House" are probably to most famous but they are wayyy overpriced. There are quite a few overpriced makers of tiny houses but keep looking. Many of them are quite easy to put together with just a a few days to a few weeks work and a few friends and tools.Just search "Tiny Houses" on Google and you will find hundreds of resources.
Many tiny houses are incredibly creative and can be built inexpensively if you put your mind to it. I have always loved them and wanted one and now we have our own 600sq ft house that we bought for less that $5000 because it needed to be moved. It's a wood frame house so jacking it up, putting it up on a flatbed trailer and moving it was tricky but my hubby did it.
Check out
http://www.panelconcepts.com/ - This is my favorite site because they give you great information on their prices, styles and optional choices. You can practically customize the model to the size you want, choose options and they have the prices right there for you to see. From what i remember, they were the site that I spent the most time at, browsing over the models and reading. They were the most reasonably priced ones too.
The website
http://tinyhouselistings.com/ is a good site just to see a vast array of little houses and their costs all over the US.
Here are some other sites to look at as well.
http://besttinyhouse.com/
http://www.pennypincherbarns.com/CabinKits/MiniCabinsTinyHouses.aspx -
http://www.zamorehomes.com/main.html - Houston based Zamore Homes makes ready-to-assemble kits built with off-the-shelf components. They're able to flat pack the pieces for easy and affordable shipping. Units range in size from small studios to 3-bedroom homes
http://www.shelter-kit.com/index.php - If you really plan to DIY a kit house, take a look at Shelter Kit. Shelter Kit includes a detailed Construction Manual, which includes drawings and step-by-step instructions, specifically created for each customer's kit. Invite the gang over for a good old fashioned house raising!
http://bungalowinabox.com/ - This Woolwich, Maine based company creates weathertight panel frame structures. With pre-cut components, you can quickly assemble cottages, camps, garages, home offices and studios. Units can be built on an onsite foundation in a matter of days.