Simple to make. I'm $180 into the project, for everything. You need to make a 'cell' and power it up with DC. 2 Parts Hydrogen and 1 part Oxygen come out of the tip. HHO, also called Browns Gas.

This is fun to do, but STAY SAFE. Look into 'anti-flashback' devices. It will happen, and when it does, you'll wish you had your earplugs in!