The Horn Shark(H. francisci) is a better choice for a beginner shark, than Port Jackson's - since they are more tolerate of warmer temps (65-80F), vs. (58-75F). Horns are also a smaller species - max out under 4', and averaging about 3'. Horns are also faster grower than Port Jackson's - growing about 6" per year as juveniles, verses only about 2-3" per yr for juvenile Port Jackson's.
Port Jackson's take up to 20 years to reach their maximum adult size of about 4.5-5'. And need about 8-12 yrs to reach sexual maturity of about 30". While Port Jackson's can be kept in smaller tank as juveniles, they will eventually require a tank of at least 1,000 gallons.