The smart ones house hack and buy rentals, but the good ones know that their clients come first.

For the reason Henry mentioned, you need to screen anyone over 18 living in the house. 

I'd guess I could sell my house with ADU for 650-675.

I have 2 options:- finance the construction pre-selling the apt, and take my profits (expected to be around 700K pre-tax); or- finance the construction with a 6-7%/year loan (collateral = my house), keep the 10 units, and once the building is completed in 24 months, rent them for circa 180K/ year gross.

I advertise via Sabbatical Homes and Harvard Off-Campus Housing and insist my leases begin on Sep 1, Jan 1 or Jun 1 and end on Dec 31, May 31 or Aug 31. 

If the owner of neighboring house says its mine I would replace and ensure it is inside my property line.

I have 9 partners on the mountain house at $117,500 each, and 10 partners on the beach house at $110,000 each, and I am currently looking for a few more partners on my jungle house near La Fortuna at $110,000 where there will be a total of 7 partners. 

I'd love to hear others' opinions on this but I am a fan of making the house as attractive as you can to a potential buyer, even if that adds cost. 

I'd recommend looking for a house versus a condo.

My first house had a tenant in it when I bought the house and they just up and left and left the house in rough shape.