Create private app for 50 users

Create private app for 50 users

I am from Brazil, I live in Goiania near Brasilia Capital of Brazil.
In my church we have a project to register all young people and to follow the growth, attendance list, birthday, among others.
I already created the app in the appsheet, but I have found it difficult to disclose, because we do not have a commercial email and also would not be able to pay value for each user who access only to make the registration.
I would like to know if there is a solution that logs in through appsheet so that I specify which users will have access without having to pay a monthly fee for it?
On average under 50 application users to use and query data.

Please contact sales@appsheet.com for assistance.