Sharing finances

[TheFutureIs]

My partner is moving into my house. He owns his property and will be renting out this house. He has a car that he currently shares with the friend who lodges with him. He will be taking on 100% of the car payments (however I will gain benefits of having a car even though I won’t be driving it)
I have a DD9 who lives with me 90% of the time.

What is the best way to split our finances to protect both of our interests? He will be gaining a small amount financially through renting his house, and obviously my bills will be increasing slightly through having another adult in the house.
Our current thoughts were to look at how much bills increase by, and also what his car payments will be to try to balance these out. He wouldn’t be contributing to the mortgage as he doesn’t want any claim on my property.

Will you loose any benefits from him moving in?
Will your council tax increase?
I'd be inclined to say 50/50 on bills.
Won't the fact that his mortgage will be payed by the renters (and he won't be paying your mortgage) mean he ofsets any increase in car payments?

No loss of benefits, yes to council tax increase (we will split that 50/50) and bills will probably split 50/50
Just want it to be fair for both of us!

He lives there full time - he contributes 40-50% to the bills (excl. mortgage).

Is his rental income simply covering the mortgage and buildings insurance or will he have a surplus? He will need a ‘sinking fund’ for maintaining his property unless he plans to sell up in future.

Rental income will cover mortgage, buildings insurance and a small contingency fund for if things go wrong/break

Thank you for confirmation of what we thought was the fairest way

He pays 50% of the bills, no mortage. You have two people using electricity, food, water etc and he is just one person so you’re getting a good deal on this but considering he’s getting his mortgage on the house he owns paid it means he’s spending less than he was in his own home.