I use one of my snake rooms to incubate eggs. I have a room with adults and one with babies. Each room is kept at 81 - 83 degrees, at all times, except when the adults are being cooled of course. Each room has an oil-filled radiator looking electric heater controlled by a Helix 1500 (I think it is), and a ceiling fan. No nighttime temp drop, and no lights, except when Im in the room.
When the Corn eggs come, I put them in 6.75" x 3.25" clear deli cups with no holes in the sides. I put several pinholes, 6 - 8, in the lid with a heated sewing needle. Too small for bugs to get in, but the eggs still get air. Vermiculite/water at 50/50 by weight.
I set them on the shelf in the baby/still growing snake room, and the helix probe is hung at the level of the containers, so they are kept at 81 - 83 degrees. They hatch in 58 - 65 days. Very seldom, if at all, do I have to mist eggs or add water to containers because eggs dent.
I incubate Cornsnake, Kingsnake, and Cobra eggs the exact same way. No problems. So, I fail to see the need to build or buy an incubator.
RC