First, let me say what a kind and admirable thing you're doing. I would have loved to have someone like you on my side when my son was little. On behalf of all parents with children on the autism spectrum, I say a most sincere “thank you.”
For most of us moms and dads, our biggest challenge is finding a willing and qualified person to watch our child while we go grocery shopping, get a haircut, have a medical appointment, or go to the gym. Some caregivers aren't comfortable watching a youngster on the autism spectrum. Others don't have the necessary experience. It would make a parent nervous to leave a child in their care (I would, for example, not have felt right about leaving my son with a teenage babysitter).
Even family members might not feel up to the task of taking care of a kid on the autism spectrum. Because my son was overly sensitive to touch, sound, and light, my mother was scared to watch him. She didn't know anything about autism and got freaked out when he'd stim. I encouraged her to read about autism, but she was unwilling. Without anyone to give me a break, I often felt alone, isolated, and depressed. I never had time alone to re-charge my battery.
My son would have benefited greatly from having another adult involved in his life besides his dad and me. Because he had articulation problems, he was extremely difficult to understand for anyone who didn't spend time with him. He needed a patient soul who was willing to listen carefully and encourage him to repeat until the communication was effectively made. It could be exhausting at times.
If you read up on autism and attend informational classes, you will be such valuable support for parents. People can be so harsh to moms and dads whose kids act differently than the norm. A person who's knowledgeable can offer comfort and support, jumping in to help and not passing judgment. I was hard enough on myself as the mother of a child on the autism spectrum. The last thing I needed was more people blaming me for my kid's unusual behaviour. What I did need was someone there who really cared.