I built a small corner of my garage into a work space. I have a portable AC and space heater for temp control, the walls are lined with soundproof acoustic panels (denser than the foam in this article's pictures). the space is enclosed using some 2x4s and plywood panels (all of which can be broken down quickly and reassembled, there's nothing permanent). I built a sliding barn door.

I didn't put a huge amount of effort into the sound isolation, the acoustic panels mainly reduce echos but do nothing for low vibrations (people walking around the house, cars idling outside, airplanes). I have total control over the lighting (I don't want to see any daylight when I'm working). It can get a little stuffy if I don't turn on the AC/fan.

Personally I love working in a little space with my back to a wall. Because of the acoustic tile, many people think I'm just in a work office. I find the limited view (basically I'm looking at a monitor with a wall right behind it) keeps me from getting distracted.