I don’t want to move in

I am the sole carer for my parents and I currently live in my own place albeit I’m renting. They have been talking about transforming the garage into a room for my son and having us live with them (me in the house). On one hand it would save me a ton on money but I like my own space and I’m not sure that living with them will be healthy for any of us. At the moment they are coping well and only need minimal assistance from me however that will change in the future. I struggle with their attitudes towards each other and always end up mentally exhausted after a morning with them. I don’t know if I’m just scared or if my concerns are justified. I feel that I will be encroaching on their lives just being there 24/7 and what about me, my privacy will be gone and my freedom too. Am I being selfish?