Competitive jumping/ "second" ponies for capable pony clubbers seem to fetch a lot! I fell into the same trap as you and bought a 3yo ISH to bring on...1 year on and he is definitely not for sale! I bought him from the field unhandled as a weedy wee thing, but he was the right shape and as bold as brass. He has filled out into a lovely 4yo and is sensible but with enough "fizz" and ability to keep me interested. So with regards what to go for I reckon conformation and temperament is as good as breeding!
Sounds good, that's part of the reason why I want pre-backed! I think any more than a year with one would make it so hard to let go and I'd end up keeping it! I suppose it all depends on temperament really! But as long as I can improve and bring them on a little I should be able to work out first or second pony, it's good to know that seconds are selling...