1. Chocolate...no I'm kidding, well, not TOTALLY kidding, but.....
In no particular order....
A large, well-lit room with sturdy tables for the sewing machines & cutting mats - I get really irritated when the table shakes while I'm sewing or flexes when the rotary cutter is open!
Lots of electrical outlets and extension cords if needed.
Several, well, at least 2, ironing boards & irons.
Enough wall space for design walls so we can 'audition' our quilt blocks.
Chairs that have padded seats - or even office-type chairs that can be adjusted up & down.
Access to a fridge for cold drinks/water. Snacks - maybe even some fruit & veggies to counteract #1! If it will be an overnight retreat, nice family-style food