Current individual stock portfolio (non-retirement accounts) with holdings that might be volatile in the next few years (big tech & big oil). $51k is about 17% of the portfolio and gains on the stock holdings are already 100-200% (long-term).

If they want to sell it and have emergency funds for medical bills, seller financing likely won't appeal to them. 

I also looked at non canal homes which were a bit cheaper and they can do similar to canal homes but cost less so end up with better profitability.

Non performing assets are why the notes are so cheap and give great returns. 

Nevertheless, a facility is on the horizon and I have now started a non-profit with family to begin a secondary path.

Non-passive to achieve this level of return.Add the addition of the ADU makes the main unit rent controlled if over 15 years old.the work to add an ADU likely exceeds the effort of a brrrr that can achieve infinite return  Experienced investors are adding multiple ADUs by leveraging items like bonus density, committing units to affordable housing, etc.  

There are the obvious pros/cons of a duplex but then there are the non-obvious ones that come with being in Detroit.I actually have a fantastic article about this I can share but I'm unable to link to it in this post.

Transaction volume is basically non-existent.

I have landlord policies for my rental properties in TX and AL states, but I am not able to get an umbrella policy form my current insurance company, because I do not have car insurance and primary residence in US, as...

If you can’t do a 1031 to a non-income tax state, figure out a year when you will have lower income and tax rates ar as low as possible.