Some time ago I read an Instructible on building a Laser engraver, and decided to build one for myself, so that I could make stencils for my Airbrushing.
I did follower certain aspects of the original, I did make many changes, mainly to suit the tools available to me, the main one being the 3D printer, every part that could be made this way, was, the hardware I had to buy.
All up cost was about $250.00.
Already having the experience of building the 3D printer help a lot, I was able to avoid all the little mishaps I had.
For the electronics, I used a Raspberry Pi developer board, and a board called a Pihat developed by Protoneer, the software was linux, and QRBL..
The first laser module bought on Ebay proved to be unsuitable, so I got one from Belguim, a 200watt this works very well.