There are definitely cons that you need to think about. What works for one may not work for another.

I see two challenges. One being financial. Some providers could not afford to lose 12-13 weeks of income per year. If you have never done it any other way or are just starting out, then it isn't really a loss as you weren't earning money in the first place but to suddenly take a loss of that magnitude is not somehting that I imagine most could take. If you have a partner who earns an amazing wage to compensate this than fantastic.

Secondly, Know your market. Maybe there is a lot of competition in your area for daycare and others doing teacher only care which would mean direct competition for you making it difficult to fill your spots. I used to do daycare in a city with so many different schools and would get enquiries from teachers constantly but in my current town there are not a lot of schools and although teachers still travel out of the area to schools there is just less demand for teacher care. This is where I would worry. If there isn't enough of a demand you may sit for a long time without filling your spots. You are already losing a potential $12000+ income annually as it is, would you want to lose more because of this restriction and only have 2 or 3 kids rather than your maximum 5? This only makes your income less and then you have to figure if after expenses you are in a productive job.

By only working term time, you are restricting the amount of potential clients by a huge amount. You will not be able to cater to the needs of majority. I definitely see the pros in being at home throughout the summer, but unless your partner has an extremely good job how are you going to manage for extended periods, especially summer with ZERO income? If you dont fill your spots to the maximum, its not like you could even put money away for the summer and to be honest you would make a poor wage term time to make up for the unpaid times.

I think the idea is great but the reality is not the same across the board. gcj already said that she got a bunch of referals from her husband who IS A TEACHER. It sounds like she got the ideal walking talking advertiser and maybe in your area you could do really well but I think that is something that nobody can predict. You can know how many providers are in your area and somewhat the demand, although you haven't started yet so dont have an accurate understanding or experience to know for sure, but you can never know who is going to enquire. The majority of the economy runs 12 months of the year, so the majority of your potential clients would not be met by your services offered.

If you can make it work then go for it, I wish you the best of luck, but be prepared with a plan B to work full time as I reckon you'd notice a huge difference in how many families are lined up at your door.