You mean he told you that red knees were too much for a first time keeper? Bull snot!
Actually red knees tend to be easier than rose hair because rose hairs need to be taken to a psychologist on a monthly basis just so their keeper can figure out why the heck they won't eat, are moody all the time and seem to have a crazy look in their eyes every evening at 7:15.
Granted, red knees are more expensive to purchase than a rose hair, but then again, rose hairs are soooo common they are cheap as dirt and a lot of "sellers" can't hardly even give them away. Maybe that's why he suggested a rose hair??
As far as substrate, if the potting soil does not have vermiculite already in it, add a little bit to it to help keep it more lose so it doesn't end up packing down hard as a rock.
Myself, I prefer to use 100% sphagnum peat moss because it's cheap, light, does not pack down hard over time (especially since total container cleaning and re-set up need only be done once a year under normal circumstances) and has a good PH balance that helps to retard the growth of mold whereas potting soil can mold up pretty quick.
Yep, NV and AZ are pretty much the same when it comes to temps and such.