It depends on the precise nature of the joint ownership. If the deed identifies the interest as a joint interest with a right of survivorship than the property became 100% yours on your mother's death. If however the deed identifies the joint interest as a tenant in common interest or if the deed is silent on the nature of the joint ownership (in which case tenant in common ownership is presumed) than your mother's 1/2 interst in the home passes by intestacy to her heirs under PA law which would probably include you, your siblings, the descendants of any predeceased sibling, and your mother's spouse if living.
Regardless of how the property is titled Inheritance tax is owed to PA so you should consult with an experienced estate attorney to guide you through the analysis of your deed and the filing of the inheritance tax return.
Very truly yours,
NOTE: This answer was prepared for educational purposes only. By using this site you understand and agree that there is no attorney client relationship or confidentiality between you and the attorney responding. This site should not be used as a substitute for competent legal advice from a licensed attorney that practices in the subject area in your jurisdiction and with whom you have an attorney client relationship. The law changes frequently and varies from jurisdiction to jurisdiction. The information and materials provided are general in nature, and may not apply to a specific factual or legal circumstance described in the question or omitted from the question.
Edward's comments are correct. As for Pennsylvania Inheritance Taxes from the limited facts presentated it would seem that only 1/2 of the value of the real estate should be subject to tax.
Hope this helps.
Mr. Fromm is licensed to practice law in PA, practices in Philadelphia, and can be reached at 215-735-2336. The response herein is not legal advice and does not create an attorney/ client relationship. The response is in the form of legal education and is intended to provide general information about the matter within the question. Oftentimes the question does not include significant and important facts and timelines that if known could significantly change the reply unsuitable. Mr. Fromm strongly advises the questioner to confer with an attorney in their state in order to ensure proper advice is received.