The summer can be a difficult time to keep children occupied, but someone gave me an old doll house along with some furniture. (My friends know I like to re-purpose things so pass them on rather than throwing them out.)
We all had fun decorating it and the kids now have something to occupy them when it's too hot outside.
I didn't purchase anything for the "renovation" instead found items I already had: paint, wrapping paper for the walls, lace for curtains, paint and material for bed and furniture, I printed a fire picture and pasted it to the back of the fireplace. There was a box of odds and ends and I took door handles from doors and glued them to the front door after painting. I made blankets and throws from left over yarn.