Hi and Welcome to disABILITIES
We have a disABILITIES FAQ (see the index) which gives lots of information about
ECVs. I would suggest you read it.
However, a few short answers.
The going rental rate is $30 per day (or less). Disney will charge $40.00 but refund $10.00 when you return the
ECV. There is a savings for using an off-site comapny.
The Disney ECVs are four wheel and generally harder to maneuver than the three-wheelers from off-site companies. Your mother might go to a
WalMart or large grocery and try one out. Note they are much larger, slower, and less manueverable than rentals.
Genrally ECVs can be parked with the strolers. Remember to take the key and any valuables from the basket. However, most of the attractions the ECV can be taken through the line and left in the boarding area.