Questions About Photo Tags / Server Storage

Hi there, I have a question about photo tags and Adobe CC. But first, a little background:

Our business is a small agricultural firm. We have two employees in our marketing department. Our photos are stored on a designated drive on our local file server. All in all, we have about 100,000 assets to manage. For years, we've used Google Picasa to tag and organize photos but are looking to make a switch as we expand and grow. I've looked into various (not Adobe) Digital Asset Management software and was taken aback at the expense involved ($12K minimum, plus annual service charges). So I'm wondering, can this be done via Adobe CC? My specific questions are:

1. Do we need to change anything about our current file storage if members of our team use Adobe CC? There's presently neither desire nor need to host our media in the cloud.
2. Photo tags are the major feature. I assume Adobe programs can read our current metadata info?
3. Is the tag library shared across users? If person A tags a photo, will those tags show up for person B on a different workstation?
4. Our two-person marketing crew are our "heavy" users who need multiple Adobe apps. What about other users who just need to add photos to a library and tag them accordingly? What apps do they need to do this?

Thanks in advance for your help!

Joe