Unfortunately, your situation serves to underscore one thing: the importance of putting an estate plan in writing. Without one, your mother's oral promise of passing title to the house to
you is unenforceable in New York, as in other states.
The intent of the law is a noble one: to prevent greedy survivors from claiming property to which they have no true claim. But in your shoes, the noble aim of the law must just feel empty and unfair.
Because your mother died without a will, her property will be divided and bestowed according to the laws of intestate succession"”and as you intuit, likely divided between you and your brother if you are the closest survivors. You can apply the letter of the law against your exact family situation by visiting www.mystatewill.com/statutes/ny_law.htm. Ignore the hype on the site to see a lawyer at once or to buy a will kit, but the free intestacy calculator is interesting to use.
Beyond that, you may be entitled to recoup the value of improvements you made to your mother's property"”such as paying costs to reroof it or have a security system installed. Even those costs may be tough to repocket, however, unless you have kept receipts and impeccable records.
Otherwise, you could lobby your brother for a fair share of money to compensate you for the time and money you invested in caring for your mother. He might surprise you and agree. But if not, your best path may be simply to move on, deal with your grief"”and live knowing that you did the right thing when it mattered the most. That's worth a lot.