I went to an orthodontist from age 8-16. I had spent half my life there when I got my SECOND pair of braces off (which I had because of the orthodontist fault - he even had to eat the cost). I think they started me too young and tried experimental treatments that I'm sure was expensive and not really beneficial.
I don't know your daughter's situation, but I wouldn't start any thing until closer to 5th grade (that seemed to be a normal age for other kids to start seeing an orthodontist) or even later, like Junior High. I have always had an overbite (still do) and over-crowded teeth. My husband also has an overbite but had a huge gap that wasn't taken care of until the last couple years in high school. Both our teeth have shifted from then and mine are not as straight as they once were (over crowed still) and my husband is self-conscience of his small gap that has come back.
Our little girl has a big overbite and we're already worried about the costs of all the orthodontic treatment she'll need. I don't worry about the pain. I guess because 1. we all endured it and we're fine, 2. orthodontics are better now, and 3. there aren't nearly as many weird contraptions now as there was 20-25 years ago. If you can, get a second opinion and find out when they recommend starting treatment. Do research online and find similar situations as your daughter and compare their treatment. Also, be very careful when messing around with a child as young as your daughter's jaw. Instead of pulling teeth, they had me widen my jaw manually each week for years (talk about painful - a retainer that I expanded about a mm each week). Well, this made it easier to straighten my teeth later on, but my bite is completely messed up and I acquired TMJ because of it.
I have no advice about paying for it - I have no idea how we'll afford it when time comes. But I do think you should be as knowledgeable and informed as possible before committing to any one orthodontist. :-)