It costs me $120/year rental, and $95/ fill for Nitrogen.
Helium is about three times the price per fill.
I got my fill hose from Joe Brancato, a pleasure to work with him.
Be aware that the tanks are typically filled to 6K, but drop to 5.6K after cooling, so you don't get 6K and you can only use to 3K, so you use less than half the gass you pay for, unless you have two tanks and cascade them.
Call your local welding suppler and ask them.
Goodluck, cheers, David.
More than just a way of life.
It's not a sickness, I can quit anytime I want.
I just don't want to.
Besides, they aren't big enough yet.