The ammonia and nitrite eating bacteria in the filter can survive quite a while if the media is kept wet. Some die off but the rest become dormant and the longer they are kept without food (ammonia & nitrite) and oxygen, the longer it takes them to become active again.
But if the media dries out, the bacteria die. It sounds as though you are starting from scratch so you will need to keep an eye on your ammonia and nitrite at least twice daily.
The gravel you had off your mother - if that was wet all the time there will be some bacteria on it, but if that was dry there won't. These bacteria grow in the biofilm on every surface in the tank, but the vast majority grow inside the filter. This is because the media are designed to have a huge surface area (think of the surface of every bubble in a sponge) and because the water flow brings a constant supply of food and oxygen. There are incredibly few of these bacteria in tank water, only the odd ones that have become dislodged from their biofilm.
You said in your other post that you had your tank off your mother - that included the filter? Does she have another tank still running with fish in or was this her only tank? If she does have another, will she give you some media from the filter in that tank? If she will, that would help you a lot. You would need to transport the media from her filter to yours as if it were a fish (ie in a bag of water). Make room in your filter by taking out some old media, where the watre first enters the filter so any odd bits of biofilm that come loose get washed deeper in). Sponge can be cut up to make it fit (keep it wet while doing it!). And don't forget to buy some new media for your mother to fill the space left in her filter
But if she did give you her only tank, unless you can find someone else with a tank I'm afraid you may well find yourself doing a fish-in cycle.