Before you commit to immobility, or doing that for someone else, why not one of you volunteer or work at a nursing home? I'm not gonna say it's a bad idea, but it could be an interesting project, improve the lives of the elderly in your care, and give you both training and understanding of what it actually takes to be or care for someone in that position.
It takes either a lot of strength, great machines, or a well trained patient to get someone "too fat to get up" bathed, changed, and turned, and I do not believe most people could simply start at it without injuring themselves or their partner immediately.
3 years