After years of testing and designing, many companies including DJI and Parrot have created some awesome drones. Inspire 1 is currently the best drone from DJI and Parrot quadcopters are made on some very beautiful, light, and stable frames. However, those frames are not customizable. Mounting your own electronics on a market frame may not be possible or may require too many modifications for it to be practical.

Furthermore, there are many simple and very good frames available on websites like http://ebay.com, http://amazon.com, or even http://hobbyking.com. The cost depends on the material and the number of motors that you want to mount. Buying a frame from websites like the ones mentioned is an excellent choice; if you don't want to mess up by designing and creating your own frame using any kind of material.

In the left-hand side image (DJI HJ450 frame), the frame is made from plastic and in the right-hand side image (X450), the material used is aluminium:

The following image...