Most RVs are not designed for easy access if you're in a wheelchair, unfortunately. However, there are some great custom made vans out there...
We were inspired to hear Benjamin Woodford's RV story. Ben uses a wheelchair and the design of his RV makes it easy for him to get in and out with his wheelchair.
So, our advice would be to hunt around or, if finances allow, have a van converted to your own needs by a reputable conversion company. It can be done!