If construction doesn't start tomorrow, it should start the following day or so. I don't remember exactly how long it takes, but it shouldn't take long.
I was fortunate to have passed all four successfully. I never could keep an extra pair of clothes I didn't plan on wearing, let alone anything I thought would match what she was looking for. One time I had a schoolboy hat, Mario mustache, and a few other cute clothes. I can tell you that my character didn't look cute with what he was wearing, but Gracie said I dressed better than everybody else in town. I don't think she has any fashion sense for loving what I had on. xD
I've got another 2 to go before I can get Gracie's! I don't like to time-travel, so I'm still waiting on her next visit. I've been collecting clothing outside my house
But congrats!