By all means use the "Cloud" if:
1. You don't mind your data being accessible by anyone in the world that is connected to the web and really wants to see it.
2. You don't mind if your data could all disappear one day when the "Cloud" provider goes out of business.
3. You don't mind not being able to access your data when someone makes a mistakes at your "Cloud" provider.

If you want real secure data be a little paranoid, don't be in such a rush to jump into the clouds. Get a RAID 1 NAS system, (they can be had for $500 or less). Store your data on it. Have your partner access it via FTP when needed. He could even back up your data to a USB drive at his location. This would limit your exposure to the nastiness of the web. I will admit I don't run a business but if I did I would be very suspicious of putting my eggs into a cloud just to save a few keystrokes.