I have lived with my mother for over 15 years. The house is already paid for.. I am 50 yrs old & disabled. My sister wants to sell the house & put mother in a rest home. I will then be homeless. What are my rights in this matter?

Your rights are minimal. Assuming your mother owns the home, it is her decision whether to sell or not. The only way your sister can make this decision is if she has been given power of attorney.

If she does sell the house, the proceeds must go towards mom's care. You would have the normal tenant's rights to notice before you need to vacate.