It's not mandatory to buy coins. We will send you an email for any job which is free, and you may apply on the same.
It depends. If you are competing for a subject like Online Maths tutoring, you have a lot of competition. There is absolutely no way that a post like that will ever become free.
On the other hand, let's say that you teach Rocket science, you would have little to no competition. Therefore for a Rocket Science post, you won't need coins - just patience for 36 hours.
It also depends on the location of the student and if the post is for home tutoring or online, budget, etc.
Therefore, you will just need to try it out and see what's truth like for you.
We give you enough coins to contact 3 teachers. Once you have used these free coins, you can buy coins to contact more teachers.
If you don't want to buy coins, you can just post your requirement and relevant teachers will contact you.