ANSWER:

If it’s not very late then they must wait for the Imam. Usually, there is an agreement between the imam and his congregation represented by the Mo’athin when to give Iqamah if he is late. 

What if the imam of the masjid comes late to prayer or he is still making wudoo’ in masjid or he is on his way from his home and the time for iqaamah has came.should we wait for the imam or start the prayer by making any of the followers to lead it.because I’ve heard that the followers should seek the permission from the imam,if they have to lead congregation.