Hi Sylvia, and welcome to planDisney!
I, too, have rented a wheelchair/scooter for health reasons as well, and I have had great experiences renting from Disney directly and from some local ECV rental locations.
Electric Conveyance Vehicles (ECV) are available to rent for a fee from each
Walt Disney World Theme Park and Walt Disney World Water Parks and Disney Springs with a refundable deposit in addition to the fee. The good news is that the same price you pay at the first theme park is per day and can be used to rent an additional ECV at your next theme park on the same day; just be sure to keep your receipt handy. When I have rented an ECV/Wheelchair at Walt Disney World Resort theme parks, I have never had an issue with one being available; however, I recommend you arrive early at your first theme park, just to be on the safe side.
If you believe you will need an ECV to assist with mobility at your resort or around the Orlando area, Disney’s Featured partner, Scooterbug dot come, is an excellent choice.
I love that Disney is accommodating to all, whether we need mobility assistance or not. Please let us know if you have additional questions.
Have a magical time!
Raquel