Some good comments, if we are talking seriously re FT then a minimum of 24x is required with half decent glass so they atleast have a chance to rangefind accurately, they can always turn the mag back to shoot.
To avoid the "10 minute wonder" they need some success, as hitting what you aim at makes you smile.
Ignore the 3-9 stuff, but defo buy used as mentioned and make sure it works or they will soon get fed up.