Resident sibling paying property taxes until inherited house sale--financially fair/appropriate?

One way to look at it is to ask yourself what you would have to pay if you moved out and rented a house or apartment on your own. If the cost of doing that is comparable to the cost you pay by living in the house, it would seem that that is a reasonable price for that arrangement. In other words, consider the price of a substitutable good (namely, comparable housing).

Your arguments are not really sound from a purely financial perspective, but that doesn't mean they're not sound, it just means you probably shouldn't try to argue your case solely on the economic merits. From what you describe it sounds like essentially your mother was your landlady and let you live there rent-free to help you out in a tough time. In some sense your siblings are now your co-landlords (along with you yourself) and must decide whether they want to do the same. An extension of your logic would suggest that no landlord would need to charge rent, since the landlord must pay all the taxes/upkeep for the house regardless of whether it is rented or not. Of course this is not the case; you pay rent for the privilege of occupying the property, and the landlord uses some of that rent to pay the property taxes, building maintenance, etc. It is only by virtue of your landlords being your siblings that it makes sense to divide the expenses with them. (If your mother had been renting out her house to non-family tenants, would you consider letting the tenants stop paying rent at this point?) It certainly seems like something siblings might work out amongst themselves, but such a decision would be made with some amount of familial altruism in mind, not just financial considerations.

Ultimately, this is something that is probably better handled through discussion with your siblings. Unless you are on bad terms with them, you can hopefully raise these issues in a neutral way and get their perspective. If they understand you are going through a tough time, they may be willing to help you out, as your mother was. (Incidentally, one thing that is unclear to me from your post is the overall communication between siblings. You say you have two siblings, but you say only your sister is proposing this payment scheme. If all three of you are co-owners of the property, you all should probably be involved in these discussions.)

Your argument hinges on the hypothetical: If we were not living here, taxes and insurance would still have to be paid.

Your siblings could just as well argue that if you were not living in this house, you would have to buy a house of your own or rent an apartment. Therefore, in fairness you should pay rent to the other two siblings for the fair market value of the house, presumably reduced by 1/3 for the share of the rent that you would pay to yourself.

There are many, many people out there who would love to be able to live in a house without having to pay any rent or mortgage, just insurance and taxes. I'm one of them myself. In my humble opinion, asking you to pay the expenses associated with the house when you're the one benefitting from it sounds more than fair to me.

The fact that the others are in a position where they do not want to live in the house seems largely irrelevant to me. Would this be relevant if they were not relatives? If you went to rent an apartment, could you pick a random stranger off the street and say he should pay half the rent, because the only reason he isn't sharing this apartment with you is because he already has an apartment of his own? His likely reply would be to say, Exactly right. There's no reason for me to pay half the rent on your apartment because I'm already paying all of the rent on my own.

Your siblings are presumably paying mortgage or rent on their living space. Why should they have to pay for the house where you are living as well?

Now if it happens that you are in a position where this is a major financial strain, and your siblings have enough money that they could easily share the expense, you might approach them on this basis. I mean, to say, yes, it's fair to ask me to pay this, but I just can't afford it.

If may be that you can make a case that you are doing the family a favor by living in the house. By living there you discourage thieves and vandals, for example.

Where would you live if you were not living in this house? Let's suppose you got an apartment. What rent would you expect to pay? If it is less than the taxes and insurance on the house, that would contribute to the "helping out the family" argument. But unless this is a very big and expensive house, I think it is unlikely that you could get even a small apartment for less than the taxes and insurance. But I don't know where you live or what the housing market might be like there.

Frankly, it sounds to me like you're getting a great deal: you're getting a house to live in for a fraction of what most people pay. I wouldn't complain.

From my seat as an internet stranger, residing for property tax, insurance and utilities is more than fair to you. Unless the local real estate market is full of vacancies or the house has so much deferred maintenance that it can't rent, I figure you are still up at least several hundred dollars per month. My concern would be if this comes with strings attached: would your siblings expect you to do more than 1/3 of physical labor in the cleanout, repainting, yard work, furniture staging, etc? Are you on call 24 hours a day for plumbers or carpenters the lead sibiling arranges? That would be fine if it's something you all communicate and agree to. You don't want to be in a position of negotiating limits after several months of reduced rent.