Plenty of RAM for doing big maps esp if you raster them out when printing or saving bitmaps from the vector source. 2Gb min.

Printers depends. If always going black and white then a laser hands down. If color then its a dice up between a color laser and inkjet. Inkjets produce more photorealistic images but are a lot more faff to deal with. If commercial printing then it doesnt matter cos whatever printer you have is going to be nothing like what you going be doing the full run on. If color is important to you then think about getting a graphics card that can do hardware color calibration (most modern ones) and ensure that you have some daylight color light bulbs where you work, dont sit in a red or blue room etc and try to set up the color calibration so that your within a shot of getting on screen what you might get near to on paper via your commercial printer. Talk to them early is my best advice. Your never going to be exact but not being a million miles out is better. Read up about CMYK, Pantone reference colors, Spot Colors and ICC color profiles. Even if you dont use them at least know about them or else when you get a proof back from them it will look radically different to what you thought you gave them.