I'd concur with the previous poster that you may be better asking this in the Rotorheads section, there are lots of Offshore pilots in there. I can give you a very, very rough idea in the meantime, as I am just waiting to start with a major North Sea operator and have a few friends already working there.
Most contracts at Aberdeen seem to be 'equal time' rosters, ie working roughly 180ish days pa and starting salaries seem to vary between 47-52ish for an ab-initio. Obviously there is a seniority system like the airlines, but I was told at my interview that you can easily upgrade from FO-SFO-Capt in around 5 years, dependent of course on movement in the company or not. Captains salaries for the major operators go from 80ish upto circa 110k, plus the usual allowances for TRE etc and SFO salaries around 62-64k starting going upto 70ishk.
I'm ex-mil myself and I believe there are lots of us at the likes of Bond, which offer quicker routes to captaincy for experienced pilots, however a friend at CHC was the only ex-mil pilot in around 3 or 4 intakes of new pilots, most being ab-initios or commercial pilots.
The shifts are all different between the companies and commuting may not be an option, that said there are shifts in places like the Shetlands where you would be working 14/14 and people commute to all manner of places. Typical shifts at other operators up there include 7/7 and 12/9 etc. Working day, I am told, varies by operator but lots of earlyish starts but early finishes, eg 6-7 am lift finished around lunch. Hence, lots of time at home with no nights away, good job security, good salaries, excellent T&Cs etc
Whilst I have yet to start up there, I would agree that the T&Cs look superior to a new start in the airlines. If your son can handle living in Aberdeen (a surprisingly cosmopolitan town and beautiful countryside) then I think it appears a far better start in commercial aviation than many other locations....