Small jobs, アルバイト, are an important part of student life in Japan. For most students, this amounts to working in restaurants or shops, serving customers. For foreigners, the standard part-time job is to teach english (regardless of the nationality), or more exotic langages. A less usual part-time job is to act as acolyte for western-style weddings. Having a western guy give a true feeling to the whole ceremony. According to friends who practiced this, it pays quite well too. Here is a article on those fake priests.