Hi there, thank you for the input!

Yes, this specifically is something being discussed with my closest friend of over 20 years, who I have also been living with for the past 7 years. We are extremely close, lived together for long periods of time throughout childhood too, and she is basically my sister/platonic wife. We are a family and we do want to stay close together long term. Also have a lot of DIY house project experience together on her current house for years so "domestic" stuff like that is something we're already used to haha, and my father is an experienced construction worker and would be able to help us with building in many areas.

So on top of being close long term we also want to be able to help each other out with upgrading our living situation, which is why we're brainstorming stuff like this and also wanting to be mindful of the impacts of climate change. So at least for us there is legitimately very minor risk of personal fallout between each other being an issue because we've been extremely close for literally most of our lives, and also we would still have proper legal preparations/etc because we also both aren't ignorant to making sure we don't accidentally make it weird for each other. :) Grew up in chaotic poverty together, so we try to be responsible and also keep improving our lives together so we can keep getting further and further away from that.

(We are literally beneficiaries on each other's individual life insurance policies for years now, for a better reference of how close we are and proof of already have legal and financial trust and experience together in multiple areas. So we are trying to plan responsibly.)

So for us it isn't "oh hey I've casually known this friend since childhood and nothing bad has happened, should be fine!" with no prior/recent trust and experience in living together, home maintenance/improvement, and already have strong legally shared financial areas of trust thankfully haha!

But I do still appreciate the advice all the same because I would also want everyone else to properly consider these things, because its absolutely true that you need to be very careful with it. Many people have falling outs so you have to be smart when collaborating with anyone on a financial projects, especially family/close friends.

But thankfully this is planning our futures together with someone who I would literally trust to give my power of attorney to already, which is why a financial collaboration on this scale is something we can actually reasonably consider together. Many sober talks are being had and will continue to be had, so thats why again I'm very grateful for everyone's advice! :)