Step 18: Helium Rental
It's going to be really hard to find some helium for rental. Many people use hydrogen because it is cheaper. Do not use hydrogen! It's explosive! Currently, there is a world shortage of helium, so try your best to call a few stores. We got ours from Bayview Balloons in Connecticut. They weren't too nice to us, so I don't recommend you to go there. Use google maps and search for helium suppliers in your area. You should get about $150 for 250 cubic feet of helium. You will only need about 100 cubic feet depending on your balloon size. The 600g ballon requires 50-100 cubic feet.
Do your best!