" Your POS and your ships will be safe for ever :) "
sooo not true. a group of 10 BS can easily take out a L pos. No pos is ever "100%" safe. Not even a large pos in a class 1 wh where BS cant travel is not 100% safe.
to the OP -
if you want to live out of an orca, it is possible but make sure the orca has a cloak so it can't be scanned down. Also make sure the wh has a static that will fit an orca, It is possible to find a C3 in highsec that is not static but in fact only has static C1. Thus when the empire wh pops, you are stuck until another direct empire or C2+ wh spawns and that can take awhile.
Best method imo for the nomadic types would be to carry pos fuel, small tower and a little defense (couple guns, web and scram). Set up the small pos (takes a fraction of the time, i think around 10 mins? to anchor) throw up your defense / etc and farm to your hearts content. when you want to hop to the next wh it wont take long at all to unassemble and move out.