Economy sucks over here too, its taken me close to two years to get a job that is only part time.
I didnt actually see those other comments, so i apologise for that. In that case, you can still drop some fish food in to keep the bacteria alive, if there is any left after a week.
I live at home aswell, youre lucky to have someone willing to pay for it all really, although what happens if he suddenly decides he doesnt want to pay for it anymore?
I'm not trying to be horrible or anything like that, just making sure you know that this hobby is a long one and there are lots of little things that can trip you up along the way, and if you arent expecting them, it can be quite upsetting.
And nope, every time you change those sponges you are removing all the good bacteria, you never need to change them

better still, why dont you replace the sponges over time with cewramic media? Muich better for bacteria and quite cheap/.