I have to agree about the type of horse,
For instance my lad who was three in may is now broken in and just walking- he is at horse school!
He went because he was getting bolshy, bored so needed something 'extra' to think about!'. They think he will finish at around 18 hh now who fancies starting to back something that big.
Once he is walking, trot and canter in the school he will go out on farm tracks and then hacks... Jacking on his own and In company to teach him to go forward.
To hel will I turn him away after forking out x amount for him to be backed.
Just because they are backed and roding at three does notean they will be asked to ride on twenty metre circles, leg yield and piaffe.
It Is just about getting them out looking at real life experiences, putting it under their belt and having a horse that walks out relaxed.