Windows Phone 8.1 Development
Software
- The Windows Developer Center is your base for all things Windows and Windows Phone related 
http://dev.windows.comhttp://dev.windowsphone.com - FREE Download: Visual Studio Express 2013 for Windows
 - Visual Studio Express 2013 allows to develop apps for Windows 8.1 and Windows Phone 8.1
 - Developers using Visual Studio 2013 Professional or higher has to install Visual Studio 2013 Update 2 to add in Windows Phone 8.1 dev tools
 
PC (Hardware) Requirements
| Operating systems | Windows 8.1 (x86 or x64) | 
| Hardware | 4GB of free disk space1.5 GB of RAM (recommended)64-bit (x64) motherboard | 
| Windows Phone Emulators | Windows 8.1 Pro or higher (for Hyper-V) and Second Level Address Translation (SLAT)Minimum 4GB RAM | 
Windows Developer Account
For starting development of app you do not need Developer Account. For publishing Windows Phone and/or Windows Store apps you need to get the Developer Account
To get a Developer Account: Included if you have an MSDN subscription Free to students who have a Dreamspark subscription $19 charge per annum for individual developers, $99 for Company accounts