If your friends owns the horse, im sure she has all the supplies needed. No need to waste money, just share the stuff. You are sharing the horse so sharing the supplies shouldnt be a big deal. Plus, what if you to were to get mad at eachother or some...
Here's a few things shipping boots, polo wraps, grooming kit, first aid supplies, grooming supplies, feed equipment - buckets, scopes etc, lead rope. Leave blankets until last because of sizing.
Ebay is a good place to look. Make sure it is new in box though. You can find good equine clippers in the care/grooming section.