Hi
all the minimum hours and other info for NVFR can be found
in CAAP 15.3-2. This will also give you a rough idea of costs involved as you simply multiply those by your schools hourly rate
As for twin NVFR, I wouldn't do it unless you already have your initial twin. Most good schools will give you a night twin nvfr rating along with you MECIR if you have a NVFR as I think the only extra requirement is to do an engine failure in cruise (though I would confirm this in the CAAPs first.)
Many would argue (including myself) that NVFR is a great introduction to instrument flying and is just a whole lot of fun. Why not just enjoy the rating, save some money and worry about the twin when it's actually going to be of use, as I'm guessing you've not finished a CPL yet and a twin job is not something you'll be using straight away anyway.
A night V is also a great way to get some more command time towards your CPL as I found even the more critical friends who don't find the idea of getting up in to a light aircraft too appealing can be swayed to chipping in for a few orbits around the city
Just my two cents.
