After the Masjid has been build, it then belongs to Allah who charges all worshippers with its upkeeping and maintenance. Allah says regarding the maintenance of the mosques "إِنَّمَا يَعْمُرُ مَسَٰجِدَ ٱللَّهِ مَنْ ءَامَنَ بِٱللَّهِ وَٱلْيَوْمِ ٱلْءَاخِرِ وَأَقَامَ ٱلصَّلَوٰةَ وَءَاتَى ٱلزَّكَوٰةَ وَلَمْ يَخْشَ إِلَّا ٱللَّهَ ۖ فَعَسَىٰٓ أُوْلَٰٓئِكَ أَن يَكُونُواْ مِنَ ٱلْمُهْتَدِينَ" (التوبة 18) "The mosques of Allah shall be visited and maintained by such as believe in Allah and the Last Day, establish regular prayers, and practice regular charity, and fear none (at all) except Allah. It is they who are expected to be on true guidance." (Surah 9:18).
General maintenance of the mosque includes keeping them open for prayers, clean at all times, keeping utilities operational, and establishing regular prayers in them.