Network and remote access for home photography business

Hello All

Here's a question for all you network savvy guys and gals.

My wife has a home based photography business. Her studio is located on our property. Currently her network consists of her PC, a Motorola DSL Modem/Router from ATT and an external USB HD.

She would like to be able to access her photos that are at her studio from home, say on a laptop but I am unsure the best method for this. She needs to be able to access these images in such a way that she can post-process them in program such as Photoshop at home, and then save the image so that it updates that file in her studio when shes completed the post editing. So, basically it's like being able to edit images in 2 places while keeping the original files and the saved processed images in one central location.

I don't know if this means NAS, something in the cloud, or simply remote accessing the PC through Windows. Or perhaps some other method that I don't know about.

I consider myself to be decently informed when it comes to computer stuff but I want to get this right the first time around so I figured it best to gain insight from those who are more skilled than I before moving forward.

I would appreciate anyone and everyone's help!