it will require you to create a separate DB for user's and what not. this will give you a layer of separation and more finite control over login access. Then for your other stuff, yes have it all in one database.
This is actually a poor design, if you are looking for referential integrity.
That is, and for example only, if you don't want to able to delete a given user if there are any record s in other tables that are referencing his user id.
At a minimum, I'd want the two TABLES in the same database, so I can make cross table references easily.