if you are that set on starting a tank now AND your in wall wont be ready for the next couple years anyways, pick up a BIOCUBE or similar all in one reef ready aquarium system (check kijiji for a used one). comes with a skimmer, sufficient lighting/flow for softies.
problem with a smaller tank is the equipment you purchase for it is useless on a 120g setup.
if i were you just save and buy the BEST equipment you can for the 120g. you'll spend atleast $600 on setting up a nano reef (even a cheap one - check out nano-reef.com). Buy a Profilux Reef Controller or something you maybe didnt consider buying for you inwall with that money.
the great thing you find out about these forums is you learn alot about what not to do from the experience of others. you dont need to run a tank for a couple of years to become a decent reefer, you just need to read and observe (save some cash that way too
). There are tons of "best practises" stories and articles on this site and others and after a couple months of just absorbing tank journals you'll see a pattern as to what works well and what doesnt.