Ask HN: Which Notebook Should I buy

Hi, Please help me for the following two cases. 1. I am a Rails developer and I am planning to my a Mac Book for my daily work. I also plan to record tutorial screen casts. I will not edit the screen casts on this machine. Which is the cheapest Mac Book should I buy? I am on a constrained budget. 2. My wife is a video editor. She wants to move from using a Windows machine running Adobe Premiere Pro to Final Cut Pro. She currently edits HD videos but will need to edit 4k videos within a year. Which Apple machine should she buy? Budget is not a constraint. We can spend USD 5000-6000 if required.