I'm not a professional, but I can speak to how to do the 4x5 thing cheaply, being a cheap photographer.
There are used cameras with the movements necessary for architecture out there for less than $500. I own two, though I don't shoot architecture so I'm not sure how good/bad these are for that particular application- a Gowland Pocket View and a Meridian 45B. The Gowland is a monorail and has all movements. You rotate the graflok back by using the tripod

Some people don't like them, but for 1/50th - 1/100th the cost of a Linhof....
A Super Speed Graphic might work too. My point is just to keep looking and you can find something in your budget range. However, I will warn you that the other stuff you need (lenses, film holders, film, black t-shirt, cheap loupe, meter, shutter release) can add up if you aren't careful. If you already have a 35mm just use the meter in that. Sheet film, developed in trays, is the cheapest route though it is easy to make tubes from pvc pipe if you want. Make lensboards from pressboard with ultra-flat black spray paint.
I have a Schneider 90mm Angulon in a Linhof shutter that didn't set me back too much (I think around $200), but I don't know about anything wider in the cheap range. I got a great deal on a Schneider 150mm Symmar-S/MC on that auction site ($150) too, but, it takes some looking.
Good luck,
William