I have bought young horses from auctions... which has had mixed results. One ASH filly was wonderful, but had to be put down - snakebite. The other filly, an arab X TB X QH could kick with incredible accuracy.. she crushed a coke can in a guy's hand because the sun hit it... and there were a few other times with shiny objects and other things, but that's the best example. She was bad tempered and I resold her to someone who wanted her conformation (which is why I bought her) but thought she'd breed nice cow horses, whereas I wanted her as an eventer and hack.
Also from auction I bought a BEAUTIFUL TB mare who turned out to be in foal (bonus!) and was wonderful under saddle. She was low in cond, so being a TB I turned her out into an agistment paddock to get a nice grass belly before she got too far along - and she was hit by lightning. So no mare, no foal. I was devastated.
So no more auction horses for me.. they're bad luck!
And I'd definitely want to at least ride a horse that's broken before I bought it.
We bought our (then) unbroken mare Rosie from the paddock, we'd seen her there in a roadside paddock since she was a foal, someone we knew had had no problems with her half-sister, and Christian was already in love with her and was determined to buy her anyway, so when she came up for sale at $500 (her sire's stud fee was $800, it's $1300 now) it was an absolute no brainer. When we went to pick her up, what a mess... she was boisterous, had her owner bluffed with her big tough fat filly act, and it took us hours to catch her, then get her into the float, we ended up having to get her mother on too (this was a 4 year old horse, and it was my 21st birthday, fun!). Next time I'm not buying anything not at least properly halter broken, she was supposedly, but I very much doubt it, she had zero respect, and was difficult to control, either on top of you or trying to get away.
The only good buying experience I've had was Rusty. Bought him from horse deals, went and rode him, and then bought him. Wonderful. Easy (besides the 4 hour drive) simple... thank god!