Proper tools for architectural photography can be very expensive as daredevil123 said. They can be quite a handful to handle too if you are not experienced. I certainly did not start with FF cameras and tilt/shift lenses and I don't see that need for you to splurge on them if you are not making money out of taking photos of buildings, unless you are willing to spend.
I'm reluctant to ask you to spend too much so my advise for you is to get an low-mid range DSLR like the EOS 550D or D90, together with a wide angle like the Canon 10-22mm or Nikkor 10-24mm to start with. If you have enough working space, you can keep the perspectives in check without needing tilt/shift lenses. That would easily cost you in excess of $2k already. You'd probably want to add a 35mm or 50mm lens for taking close up details of buildings. A wide angle is useful for architectural stuff but that does not mean you are limited to those.
Here's some examples of architectural shots taken with a variety of lenses. Hopefully, you can identify your area of interest and purchase your equipment accordingly.
Sometimes, its not even necessary to correct the perspective. A wide angle lens, when used properly, can be used to accentuate perspective distortions to create a dynamic composition. This was taken at 14mm.
With generous working distance, you don't need tilt/shift lenses to obtain corrected perspectives. Taken at 24mm.
Here, I used a 35mm lens to isolate the roof structure from the rest of the building.
Taken at 70mm to isolate part of the building.
At 155mm, I can do a further close up of the building's details.