Planning for an exit strategy should be included in your plans to full time. People plan for the future when they live in a house. It is no different when you decide to live your life in an RV.
They bought a new motor home in 2003 with a 20 or 25 year note. If they have to go into assisted living before it is paid for (very likely based on their age and health) they will let it be repossessed. Their thinking is that they won't need credit at that point anyway.
They wanted to full time so much that they took this route knowing there could be problems down the road. Basically they just don't think about the future because it is too disturbing to do so.
I know that these are your friends but, that is just so unacceptable and irresponsible on so many levels.