Who do they want to talk to?
That makes a big difference.
A ground-mounted vertical can work well for
ionospheric paths over longer distances, but
height is more important for short distances
(like out to 10-20 miles, the way CB was
originally intended).
For longer distances, a 2-4 element Yagi on
a ~30’ tower isn’t bad, but when 10m is open
it doesn’t take a lot of power or antenna gain
to cover long distances. (And when the band
isn’t open, it might not help anyway.)
What is their budget? An old CB antenna usually
can be adapted for 10m, or 10’ of Romex wire
will build a ground plane or hang off the eaves
of the house. A piece of black ABS pipe (lighter
and stiffer than PVC, but probably needs guy
ropes) can serve as a mast.
If money is no object, they can put up a big
tower with a stack of yagis on it.
More ideas? Here is a
whole bunch of 10m designsfrom the late W4RNL.