It's not worth buying. Buy a 40 gallon breeder tank and buy or build equipment for that.
Small tanks are very unforgiving, and because of the smaller size, require much more maintenance than larger tanks.
If you're definitely doing a nano, then they're good tanks, just replace the pump, the lights, add additional flow, and buy a skimmer that fits into the back. Then you'll get more comfortable with the tank. They will grow corals though. Check out my tank thread (though FYI I've never used the stock lights, I bought my tank second-hand with aftermarket LEDs already installed in it)