Building your own camper can be one of the most rewarding and fullfilling things that you will ever do. It can also be much cheaper than going out to an RV lot and picking out a brand new camper trailer or vehicle. If you have a vehicle that you would like to make into a camper, you may have to spend a lot and not have a lot of options if you have a non standard or unpopular type of camping vehicle. Creating your own camper using free DIY camper plans allows you to save money and customise your camper to your exact needs.
Check out this woodworkers enthusiast website:
There are countless links to different free camper plans that you can use and modify to achieve exactly what you want.
Use free magazine articles or access newer magazine in the archives of your local library. The link below is for a DIY camper trailer printed in Popular Science in 1946.
Search the Internet for blogs written by people who are building their own campers. For example this man build a camper for the bed in his pickup truck and includes on his blog all the materials he used, what he did at each steps and pictures of the process: http://homebuilt-trkcamper.blogspot.com/
Check out Cheap RV Living. There are many different pages that describe how to plan out your camper if you plan on camping in a cargo van. This is a great example: