Building your own camera crane is not as hard as you think. I scoured the internet for examples and came up with a solution based on the materials I had at my disposal. There are many different styles of crane to make and many different materials to choose from. My steps are meant to show you the basics of this build. I have not gone into extreme detail because, you're not likely to build an identical model. Please use this instructable as inspiration for your own model.
Before you start your own build, decide on your budget and the type of shots you would like to achieve. When you do your research, you'll notice that some models feature different pan and tilt options which is sometimes based on the number of poles you decide to use for your build.
Here are some quick links for some of the ideas I sourced.