Well its not that bad, it happened to me and made me to move out earlier.
The new flat was more conveniently priced and much closer to work. a mile and a half. Walk-able in our times.
It's understandable if you move out early if that's happened to you, because it's certainly not ideal for a parent to demand rent from their child just because they live with them. Children are a blessing to parents, and parents won't be lonely if they have children living with them, especially if the child already has a job that earns money, which can also help them a bit because the child has an income. So it seems odd that a parent would intentionally demand rent from their child just because they live with them.
It really depends on the whole situation. A parent won't demand a rent if they are not financially struggling themselves. They won't ask something for their children as long as they can bear what they are going through.
It's up to your perception how you will understand the reason why they ask you for rent or money. For me, there is nothing wrong if they ask me some money when they see me I am able to earn myself. Renting and living alone is more expensive plus you have to do all things by yourself.