Personally, I would recommend some type of filter, even a small cheapie thing. My reasoning is that if this is used as a QT tank, you *may* wind up with some form of diseases, especially if there was something lurking at the LFS. Filtration can help improve the water quality, which is necessary if you want the fish to have any form of immune system. Also, most diseases or parasites you do wind up with; the medications used will require some form of aeration or filtration. If this is the case, you would be forced to get a filter running in there before you can begin treatment; as without it, you might end up with a higher rate of fish loss, possibly simply due to incorrect treatment protocols.
Also without adequate filtration, you run a higher risk of never achieving your biological cycle, which can increase the risk of some form of toxic spike. Some of the more sensitive fish may be less likely to survive this. Depending on the number of fish you have in QT at one time, these spikes can occur rather quickly - which may then require more than just daily water changes.