Hey, How about one dongle or modem at home, but net can be accessed with all devices (laptop & mobile) that too in a secured network! Maybe some you might have tried and some did achieve it too, but there would be some who might have failed in achieving it, and others just not aware that this can be done!
Final Result: Laptop connected with Internet Dongle/Modem acts as a wireless router, where in you can access the internet of the same through another laptop/smartphone without any wired connection.
How to achieve it? (This is for Windows 7 OS)
For Windows 8 Laptops read: Wi-Fi HotSpot on Windows 8