Legal Question in Wills and Trusts in Pennsylvania

It does not matter that your friend care for his mother full time. The friend's mother obviously did not think this entitled him to any special consideration so I am not sure why you think its relevant. Further, no attorney can ethically discuss your friend's situation with you.

What would be relevant to know is when the mother died, where she lived at the time of her death, whether she had a will (you say she did) and who is the personal representative.

Unless there is a will providing that your friend can stay in the home rent free, then he can't. But he may be able to make a deal with the personal representative to stay in the house for a short time and have the rent either be deducted from his share or he can pay for the rent and utilities to the home. The problem is that the personal representative is tasked with making sure no damage occurs to the property and it will be much easier to sell if its vacant. Also, who is going to pay for insurance, utilities and maintenance on the home?

If your friend is not the personal representative, your friend and his siblings and the personal representative should get to together to try to work out an option here.