I originally had the thought and opportunity to do so in Reno/Sparks in 2015 but didn't move on it.

Renovated it, lived in it for 2 years then moved on.

I have debated about moving a house onto the property and either selling or renting the property or subdividing the property with multiple homes or even several tiny homes.

if your projects were profitable, why not find other investors and pay them the loan and move on? 

Additionally, if he’s legally and financially tied to the property, it might limit his flexibility if he wants to make major life changes, like moving or starting his own investment ventures.Ultimately, the decision depends on how involved you want him to be in the financial side of the property and how much risk he’s willing to take. 

Some will let you rent your primary and still do a DSCR loan on the subject, however, this would come with the added scrutiny of really documenting and evidencing you have no intention of moving in to the subject.  

Do they want to move?

Leveraging your equity through a HELOC or cash-out refinance can be a smart move, but it depends on your risk tolerance and goals.

That's how we also learn and develop.Make your next move your best move.

I wouldn't take that money to buy him out I'd liquidate and move into better asset class like extended stay development or 3 story walk up apartments