I said I cannot do this so I will probably just do a 5 gallon gallon or a 10.
Keep in mind this will really limit fish options. And I went back through this thread and cannot find where the parameters were given, so that is something to sort out before you buy a small tank. What is the GH and pH of your tap water?
Soft water will give you more options than hard water with a 10g. A 5g is really not suitable to anything but a male betta.