-- The other problem that you will have is that there are almost no DLP projectors that will have enough light output to give you a bright enough image on a screen larger than 128" - 130" diagonal (16:9 aspect ratio).
You need to read the projector reviews to determine what projectors are suitable, and how big a screen you can actually use (see www.projectorreviews.com
, for instance). A small screen in a small room will look just as big as a large screen in a large room. If you can find a house that has a suitable room (few windows) that is at least 12' wide and 18" (or more) long that would be very good. You want to avoid rooms that are even ratios (length to width), like 24 x 12 or 26 x 13 (which mine is) - terrible room resonances for audio, below 80Hz. It also is nice to have about 2' on each side of the screen (for speakers, etc.), that will also limit screen size.
For your reference, I'm using a 106", 16:9 screen in my 26' x 13' room. The screen is a pull-down type mounted 4' off of my front wall (where the speakers and regular TV are - about a foot from the front wall windows, draped). I sit about 11' from the screen, and that makes for a nice viewing setup (no SDE with a 720p DLP PJ). The back part of the room is used for other purposes and includes the side and rear channels of my 7.1 surround sound system and the projector. With some room rework, I could have room for another row of seating (now there only 2 of us). By mounting the front speakers off the wall helps to reduce my room resonances.
I've also seen a dedicated HT room that was about 9' x 12', with a 92" screen (a 96" screen would have been better though), and it was absolutely great, I sat about 6' from the screen - no SDE from a Panasonic 720p LCD PJ at 1.2 x screen width. He had a Martin-logan surround sound system and a Stewart Grayhawk screen which also helped the illusion.