Welcome, and I hope you have fun with your multiboxing.

I play 6 accounts, 3 of which were started by me and 3 other from friends who moved on from WoW.
If all of the accounts are not in your exact name - which they won't be since you're playing somebody else's accounts - there's a very high risk of getting them all banned as soon as a GM stops by to say "hi" after some friendly multibox hater reports you.

There are many, many, many examples of people being hit by this and Sod's Law says that it'll happen after you've hit 80 and geared up.....