Hi there, just to make sure, iRealPro does not run on Windows. It runs on iOS and Android. Having installed Bluestacks and running it on a Windows pc you basically have transformed that windows pc into an Android device. Google now thinks you're using an Android device and with a google account, a simple gmail address suffices, you are welcome in the google playstore to purchase anything. Payment through secure Paypal, provided you already have an account there, is simple. Mind: everything is to be done within the Android environment that Bluestacks provides you with. . .
in case this doubles other responses I hope you'll forgive me. . .