The database will be at least twice the size of the C/SIDE one, and you will need to have at least 2-3 times that much space for the initial transaction log when you create the database. It will probably take 3 or 4 days to create a database that big.
I did a performance tuning and training job for a client running on Navision 1.3. (about 10 years ago) They averaged 53,000 sales invoice line per day, and their database growth was “only” about 40Gig per year. Mind you, at that time the Max database size was 32 Gig, but Navision cut a “special” 64 gig license for them.