Is he too old for a first horse?

He is the most perfect horse I could ask for! He is an easy ride but also challenges me too. He is bombproof but still has the odd spook. Yet after he does something wrong he stop to see if I'm alright! He is so cute! He is a cob x connemara and he is 15. He is overweight atm because the person who had him before I started loaning him let him get really overweight. We are getting it down now. He has never had laminitis before. Is 15 the right age for a first horse or should it be younger or older? My horse loving friend told me to get a 3yo (she has been riding for 9 months and is on her 3rd horse. She just bought a 3yo who barely knew how trot.It is way to small for her anyways. She is 10 and a half stone and 5'8 and the pony is 12.1!!) But I'm not that stupid. So what do you think?