Generally the more median rental amounts $600-$1000 tend to not waiver much with market shifts because the lower income households cant afford anything more and can't get a loan as easily to buy a home.

I also hesitate to alter the dynamic of a young couples household by adding a third person to it because it has a potential major effect on a relationship.

its very tempting with all of the inventory on market there but population has been declining and average income per household is sub 30k.

See: https://dqydj.com/household-in...

The authors categorize housing prices at a median {household income} multiple of 5.1 or greater as Severely Unaffordable.  

It also depends upon your setup, whether you are renting out just a bedroom or a full separate unit with a given number of bedrooms, since different areas of the island attract different household types/sizes, though there is good general rental demand across the board and across the island.Scott Price

We are focusing on house hacking so that we can jump start our investments and live for/close to free, but duplexes are hard to come by in our area and my partner does not want to share household amenities.

Fannie Mae will allow an individual up to 10 financed properties (for households comprised of a married couple: 10 for her and 10 for him, if each spouse qualifies individually).

Though I think properties with ADU on them will see an increase in appreciation I do not think it will have much of an impact on the local housing market because:1) Not every home has space for an ADU2) Not every home with the space wants an ADU3) Not every owner who wants an ADU can afford to build oneIf ADU took off it would only help a small demographic of the housing market (i.e. those with smaller households [1 to 3 people] ).

Section 8 properties can be lucrative for a stable income, particularly in areas with a high concentration of low-income households.