Well, actually... no need to let the tank set empty for weeks; that is
not cycling. As long as the water has been dechlorinated you can put a betta in.
Letting a tank set empty does absolutely nothing to make it safer for fish, despite what we are told at the local fish store. You can find out what cycling is by reading the stickies in the beginner forum. I see you have other tanks up and running. It's a good idea for all aquarists to have a good working knowledge of the nitrogen cycle.
You can transfer an ornament or some gravel from one of your other tanks to start a bacteria colony to break down the ammonia from the fish waste into nitrates. It isn't usually considered too big a deal with such a small tank, though, since you will be doing frequent water changes anyway; but it certainly cannot hurt.
I like that the tank you are purchasing has built-in filtration. I have two the same size, which have been used to house bettas, but the thing I did not like about them is that they have undergravel filtration.
