Wheelchair-accessible ADU

I am wondering if anyone knows how to find a contractor who can advise on building a wheelchair-accessible ADU. My sister had a brain injury a few years ago and has been in a nursing facility ever since. There’s no emphasis on recovery there and its depressing as hell. We want to move her but her needs are pretty complicated. (Besides the wheelchair, she would need a care assistant with her the majority of the time plus lifts and other equipment). 

I want to find out if its feasible to build an ADU for her at my house in Richmond. Does anyone have a recommendation? Or an idea on how to find one??