Upgrade Cost From Previous MacOS Version to Sierra This is going to be a very simple and straight forward question. I do not have experience of using any MacBook. I'm a software engineer by profession and I'm considering to purchase a MacBook to get started with iOS development. I got some quotations from a local Apple Authorized Reseller and they are saying that they have 2 MacBooks that fall in my budget. Budget can be increased though. One is Apple MacBook Pro Retina 13.3" (MF839ZA/A). It has "Mac OS X Yosemite" on it. If I purchase this MacBook then can I upgrade the OS X to "Sierra"?

What will be the software upgrade costs from the following OS X versions to Sierra:


Mavericks to Sierra 
Yosemite to Sierra 
El Capitan to Sierra


What are the minimum hardware requirements or MacBook version requirements for me to install Sierra on it?

I need Sierra for XCode 8.0+.
Apple last charged for upgrades at 10.8 Mountain Lion. Major upgrades have been free of charge since then. The system requirements are publicly listed. 


https://www.apple.com/macos/how-to-upgrade/



  Mac computers introduced in late 2009 or later can be upgraded to macOS Sierra.


You can also rely on Apple providing you a clean copy of the OS that shipped with the hardware via support download if it's Lion or later. 


https://support.apple.com/en-us/HT204319