You do not wan't to make a DIY incubator to hatch out your eggs. It's a waste of time, and although not costly, it's will give you low hatch rates. The three main reasons being, 1. It's hard to maintain the correct temperatures even in an AC'ed house, the temps will still fluctuate and even going off by a few degrees, the embryos can/will die or not hatch. 2. The eggs have to be turned. You cannot just stick them in an incubator and wait for them to hatch. 3. It's also difficult to keep the humidity correct, which is also vital to successfully hatch eggs. On a DIY system you have to turn them manually by hand at least 3 times a day, or the embryo sticks to one side of the egg, then yet again does not hatch.
I've made my own DIY incubator with a dimmer/foam ice chest/ 20 watt light bulb/ some chick mesh flooring/ and a cup to try to maintain humidity. My hatch rate was about 10%.
I then decided to buy a incubator and a automatic egg turner, once I got my temps and humidity dialed in 99% almost flawless hatch rate. Huge difference and a lot of wasted time with the DIY.
I raise Cortunix quail, their care is the same as chickens (besides feed) and if you decide to keep a breeding pair or trio, they do not require a lot of space.
Hope this helps. =)