I would probably not advertise the low ratio part and just interview till you are comfortable. I have heard from people that had the opposite issue of advertising as low ratio and then when they went to fill the third and what parents thought was final spot she got the chance to take a family of 2 and took them so suddenly went from 2 to 4. She explained her business her choice but since she advertised as low ratio it somewhat committed her to upholding her end of the bargain. A lot of parents fear that rates will go up if there are too few and that is what is now happening as the new rules limit how many children parents can care for. So a parent of 2 taking in only 2 more would in the past be considered low ratio so you having none of your own at home and taking just 4 would have been too. The term doesn't really have a meaning these days and for that reason I would not worry about putting that in the ads and just fill spots till you are satisfied.