Personal preference. While paying for part of the sewer directly is ok and gives him basis (as a gift) it might make it easier for him, if audited, if you gave him the cash and he paid for it. If he were to sell in the future he would have the proof that he incurred the expense and paid for it. also, be aware that regardless of whether you pay for it directly of give him the cash these are gifts and if the value is more than $17K for 2024 you should be filing a gift tax return Form 709. Turbotax does not do this form.
