Have you considered converting a bus into an RV? They make a very reasonable platform to build on. Many of them come equipped with wheelchair lifts. I am in the process of converting my second bus to a RV.
My current project is a Bluebird rear engine.
I have seen a number of conversions that retained wheelchair lift.
Good running, well maintained buses can be had quite reasonably.
Take a look at http://www.skoolie.net and http://https://www.busconversionmagazine.com/
I purchased my current bus for $3450. Similar buses typically range in price from $4,000-$10,000. Mine had a bit of body damage that I had to deal with. It is a bit shy of 40' and is equipped with the Cummins 8.3 and Allison MD-3060.
These buses are typically very well maintained. I have seen examples of similar buses with over 300k miles and are still in service. Mine came with 170k miles. It runs and drives great.
