Buying a New mare....When is it safe to do so?

[rockin r]

I am wanting to purchasing a new mare. My question is, " when is it safe to bring a new mare into the mare barn after foaling." One of our my mares is very laid back, and her foal is 3 weeks old, (Donte). The other is not. She is the BOSS, and her foal is a week old, (Shooter). And she is very, very protective over him I can not even let them out together yet. I am in no hurry to buy. But I would like to as soon as possible. And my main concern is that no one gets hurt. My barn is good sized, and I can take down some stall walls to keep them apart until they get to know each other... Any input is greatly appreciated...Theresa