My regular hours used to be 7:30-5:30, then I pushed it to 7:45 cause I learnt that the family that was coming earliest had flexibility with their work to start whenever they wanted and everyone was coming at that time anyway (also thought I was going to be doing yoga in the morning-didn't happen, I needed my sleep more). I had one occasional mom that would drop off her two kids at 7am and I knew after doing that a few times that it wasn't for me but I do still do it on occasion-like 3 times a year. The earliest I have committed to now is 7:20. not even 7:15. I just know myself and that I really need that 5 extra minutes to get myself together So 6:30 would be crazy. In the end what matters is your quality of life.

In terms of sick days. I unfortunately don't have anything written in my contract and haven't really taken any until this past month.. am definitely going to change that upon renewal of my contract though!.
I would be very hesitant and feel super guilty to cancel on someone the morning of. I did shut down my dayhome once for 2 days to help my own kids recuperate after one of the families dropped their son off on a monday morning with Croup. I let everyone know the night before. I hoped that taught them a lesson cause he wasn't allowed back for two days, and then i shut the dayhome down for two. All other parents totally understood and didn't want their kids having croup either. Aargh...i hate it when parents drop of their sick kids. This family always did and I put up with it so long, as well as being the first ones to drop off and last ones to pick up, yet alone all their lateness. I finally was able to let them go this March after a disagreement over potty training and life is so much better. I feel like I have my dayhome back.
I say do what you know will help your life at this time. If you need the money, then sometimes wedo need to sacrifice the sleep, but if it can wait, then wait for someone that fits within your hours.