For the big room/private bath split rent into two parts: divide the common-area portion equally, then add agreed room premiums (e.g., 0, +150, +300) so it’s transparent so yeah keep utilities even unless someone WFH a lot or runs extra A/C; if so, add a small monthly adjustment from the house fund. Define shared staples (paper goods, cleaning supplies, oil/spices) that always come from the house fund, and set a reimbursement floor (ignore anything under, say, $8) to avoid nickel-and-diming. Do a quick monthly settle-up in Splitwise and rotate the autopay role every 6–12 months for transparency.
