Ah, thanks for that books. As a generality, no, I wouldn't advise that a novice rider get a 5 yr old pony. Think of a 5yr old pony as being equivalent of a teenager (in people years). 5yr old horses/ponies are renown for going through a teenage phase where they will challenge just about everything you want to do with them (and I mean everything! 
) and this can really end up in tears.
If you are a novice, then you are best going for what is called a 'been there, done that' kind of pony. He/she may not be all that pretty, may not win its class at a country show, but its done a bit of everything, is dependable, and reliable. Challenges you a little bit, but never more than you can handle for your level of development. As such, the horse/pony should be anywhere between 10-15 years old and have done (say) novice level dressage, be able to jump about 80-90cm, perhaps have done some games, be safe to hack out in company and alone, travel/truck well and be good to handle on the ground. Of course these are only the basics, and I am sure you can think of more.
If you have any pony clubs near you, there might be a horse or pony whose rider is outgrowing it and they would perhaps like to loan it out to you. That's another option. A good alternative if this is your first horse, or your first horse after a long absence from horses.
Hope this helps.