Yes it is...most of the providers I know (about 15) work this way too, and come to think of it when I was in daycare __?__ years ago my mother also did it like this.
Always ensure that your child receives quality care by taking the time to investigate the provider and by asking for references! We simply cannot verify the claims of every daycare provider.
Updates
We expect providers to keep their listing and available openings up-to-date. However, to prevent oversights, openings expire after 45 days.