I would estimate that it could double the value of the property.  

Or maybe you are thinking that when you visit your investments you can double up and see family.

@Marc ShinMake sure to double whatever they tell you it will cost and take 2x as long and then have someone to come repair all the shoddy work that was done.Hopefully you have working bathrooms otherwise you may have some surprises hidden behind your walls

If I purchase a general admission ticket for myself, can my family stay with me in the included superior deluxe double bed room?

All cities have doubled tripled or much more.

@Joseph DaviniI agreeBut I wonder where all the “housing shortage” folks and “interest rates coming down prices will double” people are?

You have considerably less wall space, and trying to fill furniture into that one big space is often awkward resulting in a lot of wasted space that does not really do anything.And while these open floorplans are often promoted as "family friendly" I have come to the conclusion that they are a double edged sword in that respect.

The second property has doubled in price and is a cash cow. 

I regret every property I sold 10 years ago (except the ones in the hood, that was a short term experiment I am glad I got out off).Your total net worth contribution is a lot higher than 0.6%, just the paydown of your loan is double digit ROI.

I remodeled and lived in three different SFH since knowing her, and prices more than doubled in there neighborhood during that time.