There's "joint legal" and "joint physical."
With joint legal, the two parents share equally in decisions on the big issues in a child's life, such as medical issues, religion, education.
With joint physical, the parties spend equal time with the child. Whether there is support money that changes hands depends on whether the time is truly split 50-50 and whether there is a disparity in income. If there IS a disparity, even if the parties share time w/the child equally, the one who makes more money will pay support to the one who makes less money.
Judges usually order joint legal custody. However, they usually do NOT order joint physical. Why not? It's really unworkable for kids who have reached school age, unless the parents get along beautifully, live in the same school district and agree on everything.
When two people are divorced, they just don't agree on things. That's why joint physical doesn't work except in very rare circumstances.
That's why judges give primary physical custody to one parent, even if they give joint legal custody to both.
The parties can AGREE to anything they want in a settlement agreement, that is later signed off on by the court, but if it goes before a judge, count on ONE parent getting primary physical custody.
Hope this helps answer your questions....