What to expect after registration

Hej, can anyone say if I will have to pay tax after arriving to Sweden for Masters studies? As the Masters takes more than a year, two years that is, I understand it is necessary to register with the Swedish tax agency and to apply for the personnummer. The personnummer would be useful to look for housing and etc. But I’m worried that once I have it, I will become a taxpayer even though I am an unemployed student and go into some debt basically. Can anybody advise me with this situation, perhaps it is not as serious as I think it is?