The ad copy suggests taking along a tarp if rain is expected, since the tent is not completely waterproof.
It
might be that giving the nylon tent a
really good spray-down with the appropriate McNetts or NikWax waterproofing
might make it reasonably waterproof. First, repeat, FIRST, I'd coat all sew-throughs with tent floor sealer, both inside and out. Doing all this will cost some money and a bit of time, though. OTOH, the tan color will help prevent you baking if using the tent in the sun. Research cost of sprays and tent floor sealer, as well as shipping. I'd guesstimate that two bottles of tent floor sealer, and three bottles of water-proofing spray should be plenty. The tent probably had such coatings originally, and might have been surplussed when the effectiveness of the coatings wore-off.
If the fairly small cost of the chemicals (any left-over can be used for other projects) and time spent is not a deterrent, and the shipping is not out of line, it
should be possible to re-hab the tent into something pretty decent. Your call. Double-check to make sure that the tent is really nylon, and not much heavier canvas.