There are some scenarios which can change the equation and take priority over the opportunity cost equation demonstrated above.  

@Bob Asad investors in high-cost areas do this all the time, but I wouldn't.They are betting on both value & rent appreciation, but it is speculation.

(Goal: either we can sell in 2 years and get the free capital gains or we can keep the great primary residence financing and rent it anytime.) 

Obviously aside from minor material cost savings the biggest reason is to save labor on all of the cutting in, which I feel would likely be moot with 3 sheens.

I have a tractor and have successfully fed wildlife before doing this.However, there is not a lot of margin to make a profit as I see bare land selling actively in MLS listings for $2-4k more than what it will cost me to buy the tax sale and do a quiet title search (likely $3k apiece). 

@Andrew GarrettI’ve been investing in NC for a while, the main issue with Raleigh is rents are low compared to costs of homes.

Your DTI will get maximized and you'll be short capex & reserves when the cost of capital is going to be higher the next 10 years than the previous 10. 

Therefore, I am interested in buying him out, but before I do I want to understand if it helps me or hurts me in my investment journey.I would be buying 60 acres for $260,000 and it would cost me $60,000 for the down payment and closing costs. 

In Milwaukee, I'd need 2 exits from the attic and 50% of the space has to have at least a 7 foot height on ceilings.Two things you want to check: both requirements are correct, but on top of that the city is getting reluctant permitting 3rd units: 50% more occupants mean 50% more water and sewer and 50% more traffic and parking.The other issue is that the cost of finishing a thrid floor with proper insulation/ventilation will run about $50-60/sf and only makes sense if you can get strong rents. 

Also, there is no correlation between anonymity and asset protection and anyone who tells you otherwise or sells you on creating unnecessarily complexed entity structures is either clueless or racking up legal fees at your expense.