House Flip is free to play, but you can buy in-game currency (HEARTS) to progress faster. HEARTS can be purchased with real money through Apple iTunes or Google Play.
To set restrictions on your device, please refer to the link:
If you would like to continue making in-app purchases but have a bit more security, you can also set the device to require your password every time you make a purchase (select "Immediately") or every fifteen minutes.