My son is 5.8 and I still don't let him play alone even in our own fenced-in backyard. So would not let him play outside by himself either. Living in a housing complex would probably make me even more worried than living in a suburbian subdivision. I let my kids explore as much as possible, we even unschool so they get a lot of freedoms but this is not one of them. Being gifties seems to make them be even more at risk (in general). Their curiosity trumps their sense of caution. Probably won't let them be out alone until I feel they are ready to be home alone too. Right now I might leave them home alone for the one minute it takes me to go get mail from the mailbox but that's about it.
