With free tuition, German universities don’t use money to determine who gets an education and who doesn’t. But they’re having a bit of a budget crunch so, if they don’t get more money from the government, the universities threatened to restrict admissions of new students for majors that don’t yet have restricted admission.
Medicine and law are two famous numerus clausus departments, with admissions depending on how many doctors and lawyers the government calculates Germany will need in x years.
An informal way German universities do restrict admission is by requiring students to pass certain highly-set hurdles in order to graduate (though you can put off graduation for a very long time while still taking classes and haunting libraries). Humanities subjects frequently require a Latin proficiency certificate. Other subjects use statistics classes for the purpose. Medical students’ ranks used to be further thinned by a notorious class in physics.
Even with free tuition, money still limits who can study and who cannot. The semesters are set up with long breaks so students can work enough to earn money for the next semester. Student rebates are provided to try to help with the costs of living and the costs of not working. The rebates I remember applied for foreign students and included low rent on well-designed student housing, cheaper mandatory health insurance (incl. dental and medicines), reduced or free public transportation (trains, buses, subways), cheaper admission to museums, movies, concerts, lakes and swimming pools…