Has anyone gone back to work while still being a full-time caregiver?

Earlier this year I had reached a state of severe burnout and was able to get away for a couple weeks, and have had my sister here to help since June. She leaves the end of Sep at which time I will have to hire caregivers for the 50 hours a week I will be gone with the new job. She can no longer be left alone even for an hour. In June she could still be left alone for a couple hours while I went to the store. I have been caring for her for 6.5 years with the past 2.5 years being 24/7 with caregivers coming in 11 hours a week and the occasional weekend respite when my other sister would visit. My sister with me now is from Az and I am so grateful that she has been able to stay this long because I broke my foot the last day of my vacation in June. The thing that is so hard is that I feel like I'm abandoning my mom by getting this job. It is a great opportunity for me and was basically handed to me with very little effort made on my part. My mom has dementia which is steadily getting worse and she has Parkinson's which is controlled by medication right now. She is still aware, knows my name but forgets my sister's name. The only medication she takes is for the PD and Tylenol for her back. I feel like I have to at least try the job and see how it goes. She is so afraid and confused, I am afraid of what will happen when my sister goes and it's strangers in her house. She has a hard time remembering the caregivers she's had for a while, one for 2 years. Financially for me to just have more caregivers come in without me going to work is an even greater financial burden on mom's finances. I wish I was able to do what I was doing, but it's just not possible if I am to keep my sanity and not have a heart attack. My health has declined dramatically over the past 3 years. Mom is physically easy to take care of but the mind stuff is exhausting and drains the life out of me. She is a "glass half empty" kind of person. I can tell her 5 things with one tiny little negative thing in there and that is what she focuses on. She's very sweet and is always thankful, which is a wonderful gift to me, but the negativity sucks the life out of me. I love her so much I would die if something happened to her at the hands of a bad caregiver. Right now I don't have anyone I can afford but have a call into someone who was recommended. Those of you who work, how do you manage it. Once my sister goes back to AZ there is no family close by to check in on her with the caregivers.