If you click on where it says "disABILTIES" at the top of this page it will take you to the Index. One of the top items is the "disABILTIES FAQ" which will gives lots of useful information, including in Post #2 where people rent ECVs.
Or, if you want an easier route to the FAQs, click on the link in my signature.
For the last ten years or so I have rented an ECV from Walker Mobility. They deliver to and pick up from the resorts (& private residences). I have used their scooters 2-3 times a year and have had excellent customer service. I highly recommend them.
I also like Walker Mobility. Had an issue with the battery dying on us one morning shortly after we arrived at the park. They were out with a new one in less than 30 minutes.