I had two horses on loan before I got the 7 month old colt delivered. I loved him to bits but made the fatal mistake of letting him get away with more than I should have. I learnt a valuble lesson that I havent repeated!
First horse was my uncles tb pregnant mare Cleopatra she was a 16'1 mare and I always put on her back and walked around I used to brush her knees bearing in mind I was 4/5 years old tops and she was 7 years old. I was given the her foal as a present for my birthday.
My first pony was a 5yo 13.2hh. Was too young probably for being my first ever pony but we got on fine, didnt have too many problems other than him being a cheeky so and so (which he still is, aged about 26!).
My first horse was an 8yo 16.2hh who was sold to me as a schoolmaster. However, turns out he wasn't and had thrown in the towel competing a long time ago... fantastic horse to ride at home and in training but put him in the ring and he just shut down no matter what we tried. Was told my a lady at a show she knew of his past and had seen his previous owners beating him up badly in the BSJA ring as a 4 and 5yo, and simply asking way too much too soon. Believe that scarred him for life! Sold him to a hacking home in the end where he still is.
My first horse (the one I got now) was 16 when I bought him, so is 17 1/2 now.
I don't regret getting an older horse as I was / am a novice and there would be no way I would have coped with him if he was younger, but, and I will be 100% honest - the time it has taken to get our relationship to where I want it to be has lead me to wish that he was a bit younger but that is only because there is so much I want to do with him!
I don't want in anyway to imply that I regret getting him - it is just that it has been a very steep, very long learning curve! (and I also, over estimated my ability and underestimated his ahem 'character'!)
Also, buying him when he was 16, I knew I would be keeping him for life as it wouldn't be fair to sell him on.
But saying all this - you wouldn't know he was 17!!
My first loan horse was a 17 year old ex-eventer who taught me more than i could ever have imagined! Th first horse i owned was a 6 year old VERY green and difficult welsh D x, who scared me half to death! All a learning experience though!