I'm all for doing what YOU know that you can handle.
I have 3 older children who are all 2 years apart. It was almost like having triplets. Now 10 years later I have my 16 month old and I knew I could handle opening my daycare and caring for all little ones his age. They all are between 11-18 months of age and its great. I have had 2 part timers that did NOT transition well (were coddled at home) that I had to let go but the group of 4 plus my own son get along great! I opened in March and they all know my routine, are completely independent (we are working on getting their own shoes, hats on, walking up and down stairs, etc) feed themselves their finger foods and cups. They are all like siblings. I have really lucked out. I am also lucky that they all still nap twice a day (1 hour in the morning, 2-3 hours in the afternoon).
I have almost an "assembly line" approach to things. Diapers changed same time, one after the other. Getting ready to go outside, same thing, meals they wait their turn at the gate to get in to their highchairs. Oh, and I make parents provide the playpens.
That said, you are the one in charge and know what YOU can handle. Maybe start of with one and see how that goes? It also depends on the temperment of the child and how the parents are. My parents are all for the most part, very laid back and are constantly asking my advice for things so trust my judgment.
Good luck to you!