Legal Question in Real Estate Law in New York

Maybe! I have not seen the document that created the life estate or set ownership as tenants in common. In the usual situation this is done by Will where a parent leaves the house to all children, but allows one child a life estate. In these instances there might be, and should be (although it might not be) some directions on what expenses are paid by whom (e.g., taxes, insurance, utilities, repairs, etc.). In the absence of any directions, it is traditional to look at the life estate like a rental, with either a rent being paid for occupancy or an allocation of expenses between the life tenant and the remaindermen. If this is not provided for, each interest has the right to seek court instructions for a determination of who is responsible for what. Of course, this can also be agreed upon between the parties themselves. The issue of the unrelated TIC is not responded to, as you seem to have accepted this person's entitlement to become a TIC. This is a response to an Internet question and the reply is not intended to be legal advice or as creating an attorney-client relationship.