Looking to build a laptop, though would consider buying a pre-built. 

My requirements are:

    1) $300 - $500 price tag
    2) Linux OS (Debian or Ubuntu)
    3) Decent Processing 
    4) Light Weight/ low profile
    
This doesn't need to be super computer. I'm mainly looking for something to play around with programming and some statistical analysis. This would also be a chance to step into the realms of a full blown linux distribution. Trying to get off the microsoft/apple bandwagons as my experience with their products continue to get worse and worse every year. Additionally I have become a big fan of Linux though my experience is limited. 

I will consider buying a pre built but do enjoy tinkering with RaspberryPis and would enjoy the project of assembly and modification. 

A bonus here would be the ability to upgrade down the road. Compatibility would also be a plus.