Well...first off, dairies do not like to sell their heifer calves. I've heard prices quoted from $300-500 for day olds, but no one knows (or says) where I can find them like that. To be honest, I would pick up heifer calves at those prices - if I could find them.
Bull calves would likely be all you could find, get, and afford. Even in my area, with the exception of calves from my boss, I can't touch holstein bull calves for under $165, most are closer to $180, and some, even day-olds, to $225! - and almost all dairies are contracted out. That means there's someone who's buying all the bull calves, and you probably would not be able to acquire any. The rumor is that there's folks in California who are buying all the holstein bull calves in the nearby states and raising them from day-olds to slaughter, and that's what's driving the prices in my area. Your area may be cheaper.
As far as dairy farmers selling calves to you, letting you raise them, and then buying them back... most dairy farmers would not consider it as it's a losing proposition. Look at it from their perspective; they sell the calf to you for, say, $500, you raise it for 2 years, probably don't put more than $700 into it in feed, and then you sell it back to them for $2000-2500. Yes that's what holstein springers are going for nationally. It just does not make sense from their end. There are some dairies that do sell all their heifers, but they're contracted out as well.
Your best bet would be to try some bull calves for starters (at least that way if you lose one it's not going to put you under) and then later when you have more experience - and connections - try for some heifers.
As to beef calves - I wish you luck. I'd raise them as well if I could find them. Dairy calves are pulled from the cow shortly after birth, which would is what makes them available as "bottle calves". Beef calves stay with the cow until 6-7 months of age, so the only beef calf you could find would be an orphan or a twin, and even those aren't available very often.