Hi. Hedge is Michelia figo sometimes called the port wine magnolia.
It depends on the soil and climate, but would easily reach 7ft in 5 years - quicker if you feed and prune properly.
The hedge in the photo is pruned by hand about 4 times a year, but hedge trimmers could be used and a once or twice yearly clip would be enough. It depends what kind of relationship you want with garden - this a plant species that can be low maintenance if needed, but is rewarding for someone who wants to get more involved.
Hope this helps.

Froglet... Many thanks for the thorough and quick response.... We are designing a home in Southern Florida on a small lot... and we dearly want privacy... and the traditional Ficus are covered with white flies... Many thanks

Hi Froglet, not sure if you are still monitoring this comment thread but do you have any suggestions on how to best prune (when and how) a Michelia Figo hedge? Appreciate any advice.

Saljen - depends on the climate. In Melbourne Australia this hedge can be trimmed lightly anytime.
As a general rule prune harder in spring for density and shape - tip prune through warmer months to maintain shape.
I also recommend pruning by hand if you have time - just because the leaves are a bit larger and by hand pruning you cut just above a n