If a horse is going to be wrecked, it's normally before he is five. Young horses are very cheap and when the time comes to begin their ridden education, there may not be enough money in the kitty to pay for the horse to be started nicely or to pay for the owner to learn how to do it themselves. The adverts on our local website are full of horses and ponies available for loan that apparently need to be broken in or schooled on. I wouldn't want to trust this important stage in their life to someone who may or may not do a good job and if I was the loaner I'd be pretty put out if the owners reclaimed the horse after I had done all that work.
In an ideal world horses and ponies wouldn't be started until they are late three or four and nothing would be rushed. They needs to be physically and mentally ready to be ridden and to have no outstanding issues with anything on the ground. This all takes time but not as much time as it takes to remedy poor training. Those early weeks need to be relaxed and enjoyable for them and not about tying them down with gadgets or working him in endless circles. It should carry on that way too......
Four to six weeks is an absolute minimum for starting a horse or pony that has already done a bit of groundwork and seen something of the world. At the end of that short period, the horse is still very green and will need lots of consolidation on non-consecutive days before he is expected to do any serious work. He is going to ask a lot of questions during the following months and those questions should not be seen as naughtiness - he is entitled to ask and to get a logical and reassuring answer.
I'm very careful about which starters I will take these days. I can't fulfil the requirements of owners who want a push button horse that rides a perfect circle in a perfect outline at the end of six weeks. I'll only take on fairly straightforward ponies where the owners are totally realistic about what can be achieved in that time and accept that we want to get it right first time. By the end of six weeks I would hope to have a pony that is happily going out on its own or in company in all the lower gears, wearing a bit, a saddle and a rider!