usability – My iPhone application requires sellers to check their email address and phone number. When should I do it?

I've been looking for the user experience before posting this question. I've seen a lot of related questions, but not this particular one. My organization creates an app that allows users to sell a service or a good. The user downloads our free iPhone application. Before you can use the application, before you can do anything, they must create an account.

We allow the oath via Facebook (by allowing them to create an account by simply pressing a button).

We also allow them to enter their name (first and last name although we plan to use a single field for the name of the user), we ask them to enter their email address and their phone number (for SMS).

My question is: When should we do this?

My instinct / intuition is that the least annoying thing to do is to ask the user to check his email address and his phone number right away, immediately before letting him do anything. We already ask them to create an account. Why not ask them immediately to check their e-mail address and phone number before letting them do anything, even to access the account.

Another member of my team feels very strongly the opposite. He thinks we let them create their account (via OAUTH via Facebook or by entering their email and phone number), but we do not require them to run the verification until we need it, like when they will create a publication for. the good or service that they sell through our application.

At the moment, there is no version of the application for consumers. Only sellers use the app to communicate directly with consumers who receive text messages and so on. when they register with a given vendor (believe it or not, this method and methodology work the same way that our vendors are grateful to have our platform to deliver their goods and services and be paid for them.)

So, should we:

A. Immediately perform the verification of email addresses and phone numbers and have them check them immediately.

OR

B. When creating the account, we send them a check of the email and phone number, but we do not ask them to complete it until we need it – like when they go make their first publication.

I like to require a correct solution for a variety of reasons, including, frankly, it's easier and less complicated to do. first before leaving them in the application.

But is it a better experience for users to be able to set up their account right away, get verification right away, but not have to complete it until we need to do it (like when they perform a publication)?

The help given to our design problem is greatly appreciated.