It is possible to use a 5m C kite as a "trainer", however it is MUCH safer to use a foil as a beginner trainer because of the fact that the foil completely collapses and depowers when the bar is released. Also, crashing an inflatable on land will probably lead to it's demise as well.
Be aware that these trainer kites can develop a lot of power and can loft you or drag you down the beach in higher wind speeds....be careful!!
I prefer to use the following trainer kites (all foils) for lessons:
HQ Beemer 3.6m
BEST 2.8m
Newtech 3.6m Ballistic
shop at
www.kitemare.com or
http://www.oceanextremesports.com/ for a good assortment of products and excellent customer support
I feel that the kites smaller than mentioned above are too twitchy and don't simulate the larger 4 line inflatables as well.
The exception to my comments would be if you have no dryland or open beach to fly a foil: such as in the Keys. In that case investing in a small bow kite might be a better use of your money, since you will probably actually want to use that kite later. Dpeneding on your weight a BEST Waroo 7m might be a good purchase if you go this route....HOWEVER...this said I WOULD STRONGLY SUGGEST A LESSON BEFORE YOU FLY THE KITE........PLEEEEAAASE!!!
In the end, assuming you are planning to kitesurf as the result of any time and money you plan on investing, going forward with a lesson from the beginning will be the fastest and safest way to reach your goals. I'll agree that flying a foil kite on your own before a lesson can be very productive, but it's not an absolute pre-requisite. I still beleive very strngly that most people will really benefit from having a 3m trainer kite (before and after a lesson) in their bag as a learning tool and a fun toy to play and progress with.
AGAIN...please take a lesson as soon as possible to keep yourself and others safe, and help us preserve access to our kitesurfing beaches.
Thanks and be SAFE.