Mum is going to need care as she gets older, which means I will give up my job to care for her. What financial support is available for me?

There are no incentives to allow people to care for parents. If your State Medicaid will pay u, like said it won't be much. And trying to set up reliable aides is not easy. Then its your future. SS goes back 35 yrs. for your benefits. So if your 65 when u retire your earnings are based on 30 up. If in that 35 years u only work 25 years, thats all your earnings are based on. So you need to consider your future.

Hopefully Mom has put some money aside or owns her home so she can be placed in a nice assisted living.

You should keep your job. Your mother should go into care in LTC when that is needed. The truth is, unless your mother is very wealthy indeed, there is no way she can pay you enough to make up for not having a job and the job you would be hiring on for is 24/7. If you have been on Forum for any amount of time here you know the mental and physical and emotional anxiety that often results. States differ in what they will pay family to be caregivers. And the fact is most caregivers we hear from at the end of both without a home and without any money or job history. We often end suggesting they go to a shelter bed and try to work up to a room in someone's home, then to a studio. For what it's worth, that would be my advice. Certainly you can check with medicaid/medicare system for your state to see what financial compensation and for what number of hours, but we are talking below minimum wage.

Why does her future need mean you will have to give up your job? If you do it is likely that whatever compensation you get for the few hours any government agency may authorize for her care will not be able to sustain an acceptable lifestyle for you. And then there is the 24 hour a day aspect and no time off. Or will she not need that much care? Reconsider your options and why you think you are the only option.