Very few homes are truly accessible, unless the person selling it to you retrofitted it for similar reasons. I believe this is going to become more common in the future, as your situation does not sound so unusual.

Some good friends of ours built an addition off of their living room when one of them started to have trouble getting up and down stairs. Their architect and builder did a beautiful job, and they referred to their home as a "ranch with a guest floor (upstairs).

Since you're in MA, here is an excellent resource:
http://www.adaptenv.org/