There are some good books on amazon you can get about architecture. I would pickup that and some basic books about photography first. If someone is paying you to do actual work, then you will want to show up with something other than a D90. Since you are a beginner I would rent from local photography store first. Try a 50mm 1.8 or 1.4 to get the feel of what a nice little prime can do. They are only few hundred dollars.