Hi there, I hope you find the answer your looking for.
I would suggest asking yourself a few questions to see which would be the best route to take?
First off how long have you been in business? how good is your rapport? if your client trusts you simply let them know that this would be mutually beneficially, it would reduce overhead for you and as stated before in this post make it cheaper for the both of you in the long run. On the other side of things if this is a new business relationship wait until that trust is there before making the suggestion. Do you want to try and push someone in a direction when your relationship is brand new, ? how profitable is the relationship for the both of you? Could the fees be worth it at first until that rapport is built that the trust is mutual. If I was paying you good money for services at that point I would already trust you, and would most certainly be open to suggestions making our relationship more profitable for the both of us.