There's really not much to go wrong...an incubator is basically an insulated box. Add a heat source and a way to control it and you're all set. Biggest question would be how many clutches do you plan to hatch? If you're only gonna have a few each year, I'd go the cooler (Coleman/Igloo, etc) route. More than that and I'd start to look at mini-fridges...
As far as a backup...having another fully functional incubator would be ideal, but some extra heat tape and a spare thermostat would get you out of any binds should the primaries malfunction...