<disregarding security>
FTP and AFP are both easy to set up at a basic levelEach of you jsut make an account for the other and then relay that accounts login info to the other. Turn on personal file sharing and ftp in System Preferences > Sharing. and youre good to go.
FTP you will have to use an ftp app for... the finder dosent work for uploading, only downloading. AFP will also work over the internet which is nice because you can mount directly from the finder.and use it as a system volume.
As for the public IP. If you have an always on boradband connection the ip thing shouldnt be too much of an issue as for the most part your ip is static... of course this assumes youre not some crazy that turns the cablemodem off when youre not using it or something. For example, until recently i had the same ip address for over a year (and i even had a couple prolonged periods of offline time for power r cable outages). If you have a router or base station between you and the modem htis is even more true as even if your computer shutsdown the ip from the ISP is still actully leased to the router as long as its on.
Furthermore there are comapnies that offer dynamic DNS which uses a program you install on your machine to notify the service of your new ip when it changes. Again if you have a router even better since most of the newer ones support some of these services - meaning you actually dont have to put anything on your box.
</disregard security>
Now i wouldnt do any of that if youre not willing to learn how to do a couple things and some basic system administration to bolster defense to all these services.
Those things include:
- ACL and permissions and ftpchroot
- some basic netinfo stuff relating to ftp and shares
- reviewing log files on a fairly regular basis
G4 Quick Silver 2002 800 Mhz Mac OS X (10.4.7)