I found a big box at work. Moms don't see garbage, we see kids toys. After all, they really just want the box, not the expensive toy inside. I've seen plenty of boxes become car garages over the summer. So why not a clubhouse?
I remember, as a kid, my mom getting a new fridge. She put the box out on the front porch until garbage day came. I cut a door and a window in it, and before I knew it, we were trying to fit 5 neighborhood kids inside. We had the whole thing colored with markers, we wrote no boys allowed on it. We, girls, did let in 2 boys at the same time by themselves, but we kicked them out after a minute.
Kids love places to call their own. Growing up in the 80's, I had a tent for over my bed that looked like a pink house. I lived in that thing. The box came later, but I was old enough to appreciate the lack of privacy you get in a family household. It only lasted a couple of days, it got too waterlogged after a good rain, and went out with the trash.
So if you ever find yourself in possession of a large box, they make the best gifts and memories.