First off he's wrong on all levels.
The Desktop Version is $29, the Server Version is $500.
A standard Mac Mini is $700 base. Mac Mini Server is $1000 base.
Second, the distributions are pretty much identical. The difference is that the Server Version ships the server applications, tools, and processes. Postfix, Dovecot, Jabberd2, OpenLDAP, the entirety of the /Applications/Server directory, and some of the things in /Applications/Utilites like XSan management and the RAID Utility.
If he's looking to do development for iOS, getting the server version makes no sense. If he's looking to do development for Web Services, it's still easier and cheaper to run it on the Desktop version.
If he's looking to run a server, trivially, for mail services, chat and calendaring services, MORE than just web services (web services are trivially easy on the Desktop Version), then he should get a MacMini Server.
Use a Server for a Server for the features it provides, otherwise, use a standard version.
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We have two versions of XServes, and two Mac Mini Servers (classic style body), I'd be glad to answer any additional questions you or your friend has.
The admin tools that OS X Server provides for DNS configuration almost justify its use on its own. Combined with your needs of email, web, and development hosting, definitely go with Server. I will assume you have the appropriate hardware for running OS X server, because a regular iMac won't do; you need either an Xserve (no longer manufactured, but available used) or a Mac Pro (a Mac Mini Server might suffice, but it will be sluggish).
Best Answer
Mac OS X Server does allow the resharing of AFP mounts but not SMB/CIFS mounts. You can however get around it by using a symlink (
ln -s /Volumes/Volume_1 /SOME/PATH) and share/SOME/PATH. While both options allow it to work it's not recommended (permissions, resource fork handling, max file size, etc. may cause hard to debug issues).Alternatively on the command line you can use
sharing(eg.sudo sharing -a path -s shareflags)