Shared Custody?

I don't know how it works in the US, but here in Canada (Quebec to be
more specific) some parents had found a way to save money on child
support that I believe is unfair for the children.

This is a true story:

A man separated from his wife. They have 2 young children of 8 and 4
yrs old. The guy is General Manager at a Sherwin-Williams chemical
coatings store and makes a pretty good salary.
He has little time to spend with the children but giving full custody
to the mother means he will have to pay full child support (Something
like $1200.00 USD per month). So, his new girlfriend who's also
separated and has shared custody, give him the idea:

- Apply for shared custody and convince your ex-wife that it's the
best things for the kids. Don't worries, if you don't have time to
take care of them just leave them with me.

The man managed to get the shared custody, and so reduce considerably
the amount of child support he was going to pay to the mother.

Find the error!