at first glance, we thought it was a duplex since it has two units and separate entrances.

I picked up the properties for a heavily discounted price (because they had sat on the market), and had no problems finding highly qualified (and high-earning) tenants that made the place cashflow right out of the gate.Another example: I once bought a property in an A class neighborhood that had an awkwardly-placed stairwell inside the front entrance, which turned off other buyers.

The low entrance bar was what got me into the SF space. 

What it cost to build a separate entrance on the second floor?

If you have a property with alley access too, that is a great separate entrance for the ADU.

It is a 2 story home with separate entrances to both floors as well as fully equipped kitchens/ living rooms on each floor.

If the house is not easily divided with separate entrances that would allow you to rent out an entire space, then you may have a great idea in moving into a smaller apartment or home while your husband gets his business running.  

That would include things like installing a wheelchair ramp, grab bars and hand rails, lowering counters to wheelchair height, assigning a parking space closer to the entrance, allowing therapy pets in an otherwise "no-pets" rental, etc.Good start here: http://massfairhousing.org/housing-discrimination/...And here: https://www.masshousing.com/portal/server.pt/docum...And here's what happens if you screw up: http://www.mass.gov/ago/news-and-updates/press-rel...

The basement is fully finished with a separate entrance, and according to the agent, can legally be converted with the installation of larger egress windows in the basement.

Purchase price: $455,000 Cash invested: $7,000 House Hacking Owner Occupied * In- Progress *Asking Price: 459,999 Rehab: $5000VA Loan 0% Dow* SELLER PAID CLOSING COSTS AND $15K IN REPAIRS, NO MONEY DWNRENT BY THE ROOM STRATEGYPITI: $3060Rent: $3500 ($875 per room, utilities, Wi-Fi, and Security System)* Current Project: 300 SQFT ADU *ADU Rent Estimate: $1800 (Includes Utilities, Wi-Fi, Security System, and private entrance, yard, and parking)Construction Budget: $20k Structure is already existing, more of a conversion What made you interested in investing in this type of deal?