I know that when a beginner buys their first horse it should be an older one, preferably above 10, because that is the age that they will be well trained and not be green. I always thought that a horse below 10 would be too hard for a beginner to ride. I am able to walk and trot, and I am improving my canter, so I would call myself a beginner, but I found out today that the horse I ride in my lessons, Charlie, is actually only 8. I always thought he was older because his is so brilliant to ride. I suppose my question is, why aren't people advised to buy/ride younger horses? Or is Charlie not like most young horses? My stables have put my on horses that they said were young and unbalanced before, but I didn't feel any difference other than being told that I couldn't canter on them (other than one horse that bucked me off but she was a rescue and had other problems...). It is that people just shouldn't own young horses, not that they shouldn't ride them?
Just being old doesn't mean that a horse is beginner safe. An older horse that has been ridden a lot will have had much more experience than a younger horse. I don't have any horses over ten years old but ALL of mine are pretty safe and well trained. My kids ride them everywhere. I have ridden horses that were well over 10 and were not safe for anyone to ride. Evaluate each horse individually but most horses that have been ridden consitently and often for 6 or more years will be pretty good horses.
Yes it's advisable for green, novice (new) riders to be on older, sane, well trained horses. Normally these horses are started at 3, get a lot of miles put on them over a few years, and are exposed to a lot of different things. This takes time. You could have a good, sane horse at 5, 6 or 7. You can also have a complete numptie at 14.
It depends on the temperment and training of the horse, not his age.
What kevinshorses said is right. The older they are, generally the more under-saddle time they have had. But I do work (I am a trail guide) with a 19 year old horse that is MUCH more high strung than our 4 year old. The 4 year old is much more stubborn but definitely more laid back and you never have to worry about her speeding up with a guest like the 19 year old may if the rider is nervous (why we try not to put nervous riders on him). Every horse has had different training, a different background, and they all have different personalities so you have to look at each horse individually.
UNfortunately too many people nowadays spoil/frighten/ruin their horse then put it on the market. I would advise making some friends who stable and show their horses. They will know of a good prospect for you, especially if it's a horse THEY would like to own. Some of the best reasons to buy what's on sale:
1) wrong color
2) too short
3) too tall
4) not fast enough
5) can't jump well, or high enough
6) not cow-y
The list can go on, but you get the idea. Remember, NOBODY sells their best horse. Many people sell their 2nd best horse, though. Don't be afraid of missing the sale of a good horse. It is a buyer's market right now, and there are plenty out there. Also, sleep on it before you buy.
Above information is all very good - but I'd also like to point out that this doesn't mean you should go running out and buy a 3 year old from the breakers. It is fair to expect a 3-4 year old to still be very green and have some 'young horse' issues still, at this point in the horse's life, it is very much 'make or break' with how they will turn out in later years. A beginner rider can go and purchase a dead quiet, seemingly bomb proof 3 year old, and turn it into a disrespectful, firey man eating monster within a matter of months.
Traditionally, once a horse reached the age of 8 it is officially "aged".
As others have mentioned, its about the individual horse. A first horse over 10 is probably a good kind of rule to stick to, both because the horse is usually more mentally mature, has had time under saddle, and the prices aren't too high. Saying that though, a horse doesn't magically become suitable because he turned ten, and many ten year olds won't be suitable for a beginner.