If you plan to live in Paris and to use public transport system, the Navigo is the affordable solution. With the Navigo pass, you can subscribe a yerly, monthly or weekly transit and you can benefit from specific prices if you are less than 26 o if you are student. More information here: http://www.ratp.fr/en/ratp/c_20585/travel-passes-and-fares/
Paris Museum Pass | Site Officiel If you’re going to be visiting a lot of museums, it’s worth investing in a Paris Museum Pass. The pass covers over 60 different museums and monuments and gives you free entry for two, four or six days. It includes the Arc de Triomphe, Sainte-Chapelle with its amazing stained glass and the sewer museum, as well as the museums listed above. Passes cost €42 for two days, €56 for 4 days or €69 for six days.