I came here on a tourist visa (valid for 3 months), then found a part time job & registered to university (M.Sc. in Mathematics & Computer Science).

Once I was registered to university I got a student's visa (valid for 1 year & renewable as long as I am still a student).

Once you manage to get a decent full time job and earn enough money (more then ~43,000 USD/year for Austria) getting an unrestricted work permission and a residency permit is not a problem.