On my recent trip to Russia, I picked up several cardboard models produced by Um Bum. Check out their website - they've got a great selection of detailed cardboard models. All the models in this photo combined came to 2000 rubles, which is less than CDN$50.
The models are detailed inside and out, and can be built very quickly with no glue, no scissors or any other tools - except the toothpick (included in the kit) to poke out small pieces. All cuts are perforated, so the pieces simply pop out.
The first model I built was the Country House No. 3 (СЕЛЬСКИЙ ДОМ №3 in Russian). This is a fairly typical rural Russian house, which could be found from the 19th Century onward. Sheets are printed on both sides in full colour on heavy card, just need to pop them out and assemble following the very clear instructions on the very clear and easy-to-follow instruction sheet! Windows are provided, with adhesive in place, just peel off the backing and stick in place.
As you can see, the interior is just as colourfully detailed as the exterior.
Here is the finished product.
The model is 1/87 (HO scale) which makes it a bit undersized for my 28mm figures, This is demonstrated in the following photos. On the other hand, it's ok to have buildings a little undersized compared to figures for most games, so these are probably fine to use as is for my WWII gaming! Reference figures are from Crusader Miniatures and Plastic Soldier Company.