I would suggest thinning down to 1.0mm, with 0.25mm grooves for the siding. That will give you (in HO scale) 7 inch thick walls and 3/4inch siding, which is still very prototypical.
Dropping from 2.0mm down to 1.0mm should halve your cost if not drop it by 75%.
If you print it in WSF, there's VERY little chance that it will crumple. WSF is actually exactly what it says.. VERY white, and surprisingly strong
On a house I had printed, I have 0.75mm diameter porch posts that are 11mm long. If pushed, they'll bend a little bit, but you'd have to apply quite a bit of pressure to get one of them to break. One post alone can support the entire weight of the building with no fears of it breaking.
If you want the Detail Material(s), you'll have to make it just slightly thicker (1.25mm walls with 0.25mm grooves) but that should still reduce your cost.