Full Stack Development SaaS

I have a sizeable following in my market and need a solution for my subscribers.

I'm looking to build a SaaS application that allows my paying users to select and auto-generate unique puzzles (sudoku, crossword, slitherlink and kakuro) and answer keys into PDFs for download 8. ---------- to-generated puzzle site example: ----------

I would like the whole thing to be in Java

I will not be needing full customization for a UI

I'd like to limit costs with premade stack solutions

FOR THE UI:
material-UI
----------

FOR THE BACKEND:
node js
----------

FOR THE DATABASE:
mongoDB atlas
----------

FOR TRANSACTIONAL EMAIL API
mailgun
----------

FOR INTERGRATION TESTING AND REDEPLOYMENT:
github actions
----------

FOR TESTING:
cypress
----------

And i'd like to use Warrior Plus as my payment gateway.

How much would that cost for the deliverable?

And how much time would it take?