what form of joint custody?
if you are talking joint physical custody - that would be were mom and dad split the time with the child 50/50. depending on the age of the child this may or may not work. one parent usually has the legal address of the child - to establish the school district the child will attend. in a personal view - joint physical can't work unless mom and dad live on the same street basically. although this seems like a dream for the parents, they spend large amount of time with the child. it is hard on the child, they don't really have an established home because they jump back and forth between mom and dad's house.
then there is joint legal custody. in most cases, the children will reside with one parent and have the standard every other weekend and rotating holidays with the other parent. both parents are suppose to discuss the decisions concerning the children. they are suppose to "parent" together.
i have seen support ordered in joint physical cases before. my brother had a support order for 250 a month for two kids, with split custody. it was suppose to balance the income of the household and ensure that the kids receive everything they would have if the parents would have stayed together.
it is rather hard to get "sole" custody of the child. especially if the other parent has had an active role in the life of the child up until now. now if the other parent just disappeared from the scene and has had not involvement whatsoever, it will be easy.