Your statement "I don't agree with their choice of life" caught my attention. Addiction is an illness, not a choice. Mental illness is also an illness, not a choice.
I understand your wanting to help, but you may also need to consider if your helping is enabling them. You are in a very difficult place, having someone you obviously care about who has co-occurring illnesses. You are not alone, there are many people in the difficult place that you are in.
I would respectfully suggest that you won't find anyone who would want a person with untreated substance use disorder and untreated mental illness, living in a trailer or shed on their property. Also, as zoning would probably not allow this to happen within city limits, your loved one may not want to relocate out of the city.
I would suggest that you look into some of the supports that are available for family and friends of people struggling with addiction. Here is a link that lists some resources that you may find helpful:
http://mbaddictionhelp.ca/services/family-friends/