
If you are buying one, buy one that will last - for me there's no point buying a small crate and I don't subscribe to all this 'confine them to a small area', re emptying in there (or not emptying in there!). At least if he's in a big area, he won't be forced to lie in it. And much as mistakes happen, I let mine out often enough so there's absolutely no need to be shut in a crate and need to be emptying in there. For me, part of learning to hold is about them learning that you will be letting a puppy out often, so he has no need to use his crate as a toilet. My puppies were always in a puppy pen, once out of the whelping box, in the kitchen but those most recently bought in were in crates in my room overnight, being taken out at least once early on. As I don't want unexpected mistakes, or to have to put up and take down crates in the kitchen (too small to leave them up where we now are), my two are still crated in my room overnight with the crates left up.
Add - No cardboard box would have worked for my Bassets, or, for that matter my Whippet who at 9 weeks would have been out of it in a second. And I prefer a proper wire crate which can be covered top and 3 sides to make a nice snug area for a puppy.