Yosemite Server: Spotlight from client
You don't need a Mac running OS X Server in order to take advantage of Spotlight.  Personally, I have a Synology NAS with AFP, SMB and NFS shares that Spotlight has indexed.  (I do avoid SMB because it is much slower than AFP or NFS)

From the client (iMac or Macbook Air) mount the shared folder as you normally would

From terminal on the client run the command:

mdutil -i Volumes/&lt;mount-point&gt;


The "-i" tells mdutil to enable indexing.  The "-s" only prints the indexing status.