Its always a good idea to have a look at the apartment you are planning to buy before parting with the cash. Even if this guide was complete, pictures are no substitute for seeing it yourself. If you're playing on TerraI'm happy to let people view any of the properties I own. Currently this is:
Plaza 'level 1' apartment
DoY 'Normal' apartment
If any players feel generous enough to purchase additional apartments for me, or to hand over apartment keys they no longer want/need I will obviously not object :-)
To be honest though, if you're looking to buy one of the 'starter' apartments, its quicker and easier to just create a new runner of the appropriate faction in order to view the apartment.
NOTE: This service is offered 'Out of character' (OOC) and therefore runners from enemy factions are able to make use of this offer. Please be aware though that, outside of this accomodation, I do role play my character(s) so they will respect their factions political standpoint and will treat other runners appropriately (so please dont think I'm suddenly ignoring you or being hostile). I therefore request that any communication between our characters be done via the 'direct' channel during any 'apartment tour'
There are several locations where you can purchase apartments, depending on which one you want.
Getting a player who specialises in the Barter skill is a great way to reduce the cost of a new apartment. Some Barter players charge a flat fee, some charge a percentage, while others have been known to just round the price up, it varies from player to player so be sure to check in advance. Just remember that, unlike other tradeskill players, these guys will have to come with you to the appropriate vendor to make the purchase (which may be a long way away from where you found them) so make sure you make it worth their while. It's also worth mentioning at this point that I believe faction sympathy has a bearing on the price your are charged, you may want to bear this in mind if you have to choose between several barter specialists.
I've seen this question come up enough times in the forums to warrant a section on it (and to be fair when I bought my first one I didnt have a clue how to find it either). When you get your hands on your key you need to right click on it and Use/Activate it and you will see a little message in the chat window confirming activation. You then need to right click on the key and Use/Activate it again, this will display a window showing you the location of the apartment and the current password (which will be blank). You need to set a password and then find the appropriate elevator. Certain elevators (notably the ones inside Neocron city) can be found by using the Nav Ray (under the 'Apartment' section) but for other zones you basically just have to open each set of elevator doors and target the interface, the name of the interface needs to match the location listed in the key info. NOTE: I know for certain that the Tech Haven interface names are different to that listed in the key, however the numbers (1A etc) are still correct. Once you find the correct elevator, enter your password and enjoy your new apartment (check the cabinets for rubbish).