Hi Scott
They are usually ok and will last if they are looked after. Would not say they are completely waterproof though. They would be light canvas so maybe not as waterproof as you would hope. Would be ok in a downpour if you had a tarp over it i reckon. For the money I can't see anything wrong with it.
You may want to check out Outback adventures online. They have lots of tents on sale in the latest catalogue.
Cheers
Ronnie