I made my incubator out of a beverage cooler. I got it on Craig's List, the guy actually bought it brand new and it was non-functional. I'm pretty sure they sent him a new one and he kept the old one so I got a screaming deal.
So many people on this forum say that they gut the freezers and beverage coolers before using as an incubator and go through the whole process of taking out all the electronics and hardware. Instead of all that I just opened up the main compartment on the bottom and simply unplugged and disconnected the electric from all of the workings of the cooler. I did leave the LED lights connected and they work great, still on the factory switches. Not sure why you would spend all the time dismantling it all when you can simply unplug electrical connections.
I've heard that a real fridge or freezer will hold better temps than a glass front cooler. But I haven't heard of anyone having problems to the degree where eggs won't hatch. Here's my incubator, I'll be using it for the first time this season. I also have a smaller scientific incubator that I can use if I fill this one up.