Hiya!
We tried the "training for your level" thing for a while. It bugged us. Not the cost or time, just the idea that an adventurer would need to stop adventuring and "attend school" in order to get better just made no sense to us. It's like someone being in the military, going into a war zone, fighting off the enemy, saving dozens of lives, gathering vital intel and then having to fly back home to take a 6 page test that includes a written essay in order to get promoted. LOL!
But all the rest?

Yup. Makes sense and I like (and use) it! Mind you, it's a bit different as I use primarily Hackmaster 4th Edition (the 1e/2e hybrid...not the latest 'new' system).
Oh, and why do people always jump to "GASP! SLAVERY!??!!" when "...or creatures sold" comes up? I'm not going to comment on my theory, but I will say this: are these not also creatures... chickens, guard dogs, horses, wolf pups, bear cubs, monkey's, dragon eggs, griffin eggs, etc? I mean, once you defeat the evil Black Heart Bandit Gang what are you going to do with the 14 riding horses, 3 war horses, 6 guard dogs, 23 chickens, 3 cows and that strange monkey with the big eyes that always give you a head ache when you look at it? Sell them, of course!
For the Record: In 5e I award only 1/3 to 1/2 (
maybe 1/1...maybe...) for defeating monsters, but I award 1:1 XP:GP for treasure recovered/gained. This puts the focus for the players on "lets 'win'..." and not "lets kill it...". When the Fighter can hack for XP, and the Thief can steal for XP, both "win" by doing what they do best. Nobody feels like they have to "ignore their class focus and just kill stuff" in order to advance in level. I think the XP:GP is the
BEST way to handle xp in a D&D-style game.
^_^
Paul L. Ming