Bonnetheads are about 14 to 15" when they are born. They don't live long so they reach sexual maturity at 2 years of age... and will generally be full grown within 4 years. They only grow to 4 or 5 feet but they need a 3,000 gallon tank to thrive. Something like 10x10x4 would work well. They are extremely temperamental and need expert care. These sharks shouldn't be owned by average hobbiests.
There are many types of reef sharks. Some aren't available to the aquarium trade because of their nature. Generally the only ones you see are Black Tips and White Tips. Both have pretty similar lifestyles so they same tank conditions work for both. The only difference is that White Tips get much larger and require a much larger tank. You can put black tips in a 6,000 gallon round tank or a 3,500 gallon sqaure/rectangle tank. Whitetips will need at least a 10,000 gallon round or a 4,000 gallon square/rectangle.
Bonnetheads are going to cost you around $600 and Black tips $500 White Tips $700. If your licensed you can get them all for around $230.
Jim