In general, this would be an acceptable practice. I have a mountain cabin
with a basement, and we have the water heater and pressure tank in the
basement. I like to be able to control the pressure tank switch, and to be
able to adjust and monitor the hi/low water pressure set points on the
pressure tank switch.
As one post said, special considerations would have to be given if the water
heater is a gas one (elevate off floor) and you want to be sure that the
basement or garage area will not drop well below freezing, as that could
create problems for the water heater, pressure tank, and water softner.
But, these same freezing considerations would have to be accounted for if
these items were placed outside as well.
If it were me, I would put those items in the garage, or in a basement if
you will have one !!
Hope this helps !!