When I said 3-5 days that is only if you use a "seeded" filter media from one of your other tanks to push the cycle along quicker. If you are not used to cycling tanks without testing the waters I would still test the water, or whatever you need to do to feel comfortable, but if you use a substantial chunk of seeded filter media there is a good bit of good bacteria if you LIGHTLY stock the tank, such as with one betta only, for a week or so after adding the betta.
Your main goal is to slowly increase the bioload of any tank until you get it where you want it (as long as you do not want it overstocked

) so that the good bacteria has time to build up to combat each level of bioload as it gets greater.
