Mom has a brain tumor. Can I get financial help, I'd personally like to take care of her myself.

If your mom is on Medicare/Medicaid and has other insurance, call those agencies to see what help is offered in your state. The government doesn’t allocate much to pay caregivers, if anything at all.

if your mom is able, she can pay you herself. You will have to draw up a Caregiver’s Agreement which you can find by searching on this site.