There is both joint legal custody and joint physical custody. Joint legal custody means that both parents jointly make major decisions in the child's life such as those pertaining to religion, education, medical needs, etc. Physical custody pertains to the physical time the child spends with each parent. The parents can jointly agree to a custody order. If the parties are not able to come to an agreement regarding both legal and physical custody, a judge will make that determination.
Judges take account of varying incomes and award child support accordingly.
One parties' income should not affect a custody decision. Again, the court considers what would be in the children's best interests, and will set visitation accordingly. If the parties are able to settle the case out of court, the parties will jointly determine all visitation schedules. The court will almost always adopt any agreement reached by the parents as the order of the court.