How many followers to start earning from shoutouts

How many followers do I need to start receiving offers for shoutouts on instagram. Also what is the most profitable niche, is it traveling?

My plan is to start 30 accounts in traveling niche so if I receive only one offer per account monthly it means that I will have daily income. After few months I will probably hire someone to manage it daily. On this way I will convert it to passive income.

Is this good idea?