Haha! Yes, hello. My polycule cohabitates, has joint finances and owns a house together. We are actually right smack in the middle of plying through paperwork again, so my blog will have updates on that. We are not a triad, but a V. None of this has necessitated a lawyer. Here's what we currently have:
My husband DarkKnight and I are legally married. I have legally changed my name through the courts to reflect both PunkRock and DarkKnight's last name.
So my legal name is Bluebird Rock Knight, if that makes sense.
Finances: Each guy has his own separate savings and checking account. Each of them have a paycheck direct deposited there. Each payday, they transfer funds into a joint checking account, which is managed by me. I pay all joint bills: Mortgage, car payment, car insurance, car maintenance & repairs, electric, gas heat, internet, Netflix, life insurance, cell phones, pet care and clothing. The car maintenance and clothing are preplanned, meaning that I will be told ahead of time that DarkKnight will need new sneakers, or that PunkRock's car will need an oil change next month. So I budget accordingly. Usually when we go out to eat, I pay from the joint account as well. Vacations are paid from the joint account, though each guy usually will add in funds to pay for extra if he wants to do something extraordinarily expensive, or in addition to what was already budgeted. Anything left over in the joint account is my fun money. The guys have what is left in their individual account to play with - this way there aren't arguments over who spent what. No one gives a shit if PunkRock bought 10 new board games this month - he spent his own money.
Retirement: DarkKnight's 401k pays out to me, as does PunkRock's, if they die prior to me. I don't have one, having been a stay at home mom for many years.
Life Insurance: This is something we are changing right now, so it is in flux. I am primary beneficiary to DarkKnight, and PunkRock is secondary, in case DK & I passed at the same time. PunkRock dies, I benefit first, and again, if PR & I die at the same time, DarkKnight collects. If I were to pass, both DK & PR each get 50% of the my policy. We all have policies that will cover our final expenses (cremation) and our current outstanding debt.
Since we recently bought a house, we were waiting for that to be handled prior to increasing insurance, so that is why we are in flux at the moment.

The idea is to have both DarkKnight & PunkRock have an individual policy that will pay off the mortgage 100% if they die. My policy will be the amount of the mortgage x2, so the house can be paid off, and then they each will have half the value of the home left in cash, so they can buy out the other and move away if they do not want to continue to be roommates. This way one person can keep the house and not be compelled to sell just so the other person can cash out their equity, if that makes sense. Numbers, as an example: Let's say the mortgage is $200,000. I would need a $400,000 policy. I die, and the house is paid off, with DarkKnight and PunkRock each then having $100,000 each. DarkKnight decides he wants to move to Alaska, so PunkRock then buys out DK's half share on the house. If PunkRock didn't have that $100,000, then he would have been forced to sell the house to pay off DarkKnight. We don't want that to happen, though in all likelihood they would continue to live together because Alaska is cold. Lol
Medical: We all have living wills. In our state, we have to re-up them every year, but that isn't difficult - we just print new forms, sign them and put them in the safe. All of us want to be cremated, and all of us have specified what
we'd like done with those. PunkRock is my health care proxy. DarkKnight can be by my side in the hospital because he is my legal husband, but since PunkRock has no paperwork proving his marriage to me (bigamy is illegal), him being my proxy means that no one can bar him from my side. I am health care proxy to both DarkKnight and PunkRock. The doctor's office has both guys listed on my file as my spouse and in case of emergency contact.
Health insurance - I am listed on DarkKnight's policy, PunkRock has his own policy. To do otherwise would end us up in legal trouble.
Home Ownership: We decided to do this easy - DarkKnight is the only one on the mortgage and on the title. He provided 100% of the downpayment. PunkRock has put in months and months of sweat equity (he has knowledge, know-how and skills). We decided that if there is a split prior to 5 years, DarkKnight gets the house 100%. After 5 years, the house will be sold and split 3 ways equally. If someone doesn't want to sell, then the person looking to leave would need to pay for an appraisal, and then the other two would pay 1/3 of that to "buy out" that partner. We are still working on this paperwork - we will get it looked at by a lawyer eventually.
Family Planning: I have two children from a previous marriage who are grown and out of the house. DarkKnight and I have a child who is almost 20, and who will be moved out in a few months. PunkRock has no children. No one in our polycule is having any more children. All of the kids are aware of the paperwork we have in place and understand that inheritance will only happen after all 3 of us have passed.
Our lives are generally pretty low key and we don't fight about money. We meet once a year and have an official "State of the Union" session where I lay out what we've spent, big expenses coming up, and long term goals we are working on. We also talk about budget adjustments that may need to be made. For example, we knew PunkRock needed two surgeries this year and would be out on disability for a month or so. This meant that no one would be going on a summer vacation out of state, because all cash would have to be focused on paying the regular bills while he wasn't getting paid. This wasn't an issue for DarkKnight, because he isn't an asshole. However, he knew about this since last year, so we worked through all concerns then. No surprises!
I am not a lawyer. I can only say what we've done and so far it has worked well for us!