Hidden items Game built in unity

Hello,

I want to built a game with below features.
Visitor will register and take membership.
Then he will be a paid user.
There are different locations in the screen using MAP or place icon
User click on it and unhide the items
There will be multiple level with some in-app purchase for solve the game, there will be timer for the level.
I will add and active/inactive more places from the users depending on the membership plan

Kindly give me an estimation of first time development and then addition of each location.

Also mention the server expense to host this game (if anyone have the knowledge)

I am not sure about the budget (give your best price)

Thanks & Regards,
Tushar