How to create a home office with remote access to all your files...

First things first get yourself a good NAS device. Install it on your home network. I have found Synology** works well and has all the features you will need. Get a NAS with at least 2 disks and make sure that it has RAID 1 or greater to protect the disks. Use a UPS to protect it from brown outs and surges.

Create a DropBox, GoogleDrive or Box Cloud File Storage account to store your files on. If you have less than 5GB of files (or whatever the limit is for the service) you can get away with having a free account.

Synology has a CloudSync component that you can set to sync you cloud accounts onto the NAS disks. Install it on your Synology NAS and add your online storage services to Cloudsync and put the folders in a place on the Synology that you can share them with the local network users who have PC's and laptops.

On the Synology you will  need to enable file sharing for Windows (SMB) and if you use Macs (AFP) and share the parent folder of your  Cloudsync root folder. This allows your users on the home network to edit and upload files and then the Cloud File Storage Account will mirror them up to the internet to allow mobile users to have them available from anywhere.

On your mobile devices add the Cloud File Storage Account client (I think I would recommend using Dropbox as it's very mature stable and doesn't take over the mobile device like Google Accounts do). Add the account on each mobile device that needs access to the same "home office" files.

The above gives you road warrior on-a-budget access to your home office files. It should cost under $1000AUD if you DIY.

** Whatever you do don't buy a Netgear ReadyNAS, bad bad bad.