You would both only need the one pump.
These are real air movers.
I run all of my outside tanks, 4 rooms, with one.
Cost?
start saving, they aren't cheap.
You can get them from your LFS.
Get a price and let me know,
I may be able to wangle something for either or both of you.
I bought mine second hand, and can't remember what I paid, sorry.
Alan 104