However, in the U.S. the preference is to (eventually) live independently of your parents and in-laws as healthy boundaries are established.Interestingly, much of the value of residential real estate has been historically created by the exchange of longer terms benefits such as a homeowner might receive from a lender, or an SFR tenant might trade with a landlord.

Which architect are you usingWhich GC are you using Are the soil reports done on the property already or is that another cost and variable you are unfamiliar with What kind of material do you want to use I can go on but I'm sure you get the idea. 

I know they are insanely expensive, but a septic system that is effectively a waste treatment plant can function in almost any soil.  

I'm not familiar with you specific area, but one has to wonder just how healthy the rental market is there.

Equity, healthy reserves to cover the unexpected, some cash to take advantage of unexpected and outstanding opportunities, and perhaps as important as these things, a steady hand and a healthy longer-term perspective.

that would definitely violate housekeeping and maintaining a healthy environment.  

Make sure to keep a healthy dose of skepticism handy without becoming cynical.As you are already a landlord, you are familiar with some / many of the issues that come with the rental ownership.

What would you consider to be a healthy split for a partnership?

We are healthy, active retirees and do our own management, maintenance and landscaping. 

.- If you want to be healthy, learn to love fasting.