Is this something you've ever done as an individual landlord, or is this something more for larger multi-family properties only? 

I prefer individualized service myself.  

But he chose that one over the others because it was very user friendly (for our older managers) and it offered a 'Groups' function where we could add certain individuals to different projects.

If someone stays at a property for 14 consecutive days or more, they could potentially be considered a tenant under state law, even if their stay is structured as short-term renewals.If the individual is classified as a tenant, landlord-tenant laws would apply, meaning you may need to follow formal eviction procedures to remove them.

Individualized container homes would be ill suited for assisted living style care.

First thoughts are finding a way for the tenants to use it for a fee, either rent the space monthly or create a space that can be rented on a per-use basis....or possibly rent to another non-tenant individual for office use of some kind. 

Be sure to factor in management complexity, market research, and your risk tolerance as you evaluate options.Without a W-2, HELOC approval can be tricky, but some lenders will work with retired individuals, mainly if you can document stable income (rental income, retirement funds, etc.).

Median individual income is 25K a year, and the median rent is $1200/mo.

- I guess I could sell the individual units.

And as others said, section 8 tenants are often the most quiet and reliable because they don't want to lose this aid and they are grateful to have housing.