I'm a designer with CS 5.1 and I need to find the best option of Photoshop for my UI Developers. They would just basically need "readable" capabilities by taking my PSD mockups and view things like font sizes/weights, color hex's, pixel sizes, etc. for implementation. Is there any basic/cheap form of photoshop that will be a Mac CS 5.1 compatible for a Windows computer?
Your Photoshop CS 5 files are perfectly intact and readable on Photoshop CC (it's just two versions up) Windows or Mac.
Photoshop CC files should be perfectly intact and readable in Photoshop CS 5.1, but if they use a feature or filter not found in CS 5.1,you will be able to see it but not edit it.
You may want to go into Preferences > File handling to be sure extensions and thumbnails are there for Windows.
For example Windows won't know what program to open the file "mock-up" unless the .psd extension is there.