I have one guest bedroom that is almost always available (queen). There is also a second bedroom where my younger son sleeps when he is at my house (twin). It's available about half the time. But I also have inflatable beds and a finished basement (heat and A/C), so it would be easy to find room for an extra child anytime. Plenty of toys for kids (2-12). Near good parks. You are welcome to use kitchen + living room. Walk to the red line, green line, grocery stores, Harvard, MIT, and BU.