With such a big chunk of money going elsewhere every month, that's making it tough for parents to sustain a retirement fund.

Although many millennials are drowning in student debt and need the help, it's not as if their parents have unlimited funds available to throw as a life preserver; the Kaiser Family Foundation says that approximately 57percent of Medicare beneficiaries 65 and over have incomes of just $29,999 and under, and only 21 percent have incomes of $50,000 and over from which to dispense their largesse.

So what should those parents be doing?

The report says that parents should figure out just how much they're prepared to do to help out, both before and after college, by figuring out what that help will do to their retirement savings plan, lest the parents end up giving away the store and discovering too late that they've crippled their own futures while helping the kids build theirs.

Knowing the numbers will help parents, and kids, to figure out strategies that might work—like a loan from parents instead of just a handout, with the kids paying it back as their careers take off and supplementing their parents' retirement funds.

Parents also ought to tell the kids, before they even head off to college, just what the parents are prepared to do to help out—and if they're not going to provide financial support, tell them up front.

Kids who head off to an expensive area, whether for college or a job, might have to be prepared to live with roommates, while kids who take low-paying jobs after college will have to steel themselves to live with student debt for a longer period of time.

Otherwise kids will be expecting more than they're going to get,

And once the kids have graduated and are on their own (well, except for that parental financial assistance), parents have a right to insist on accountability and put limitations on how much and how long they're willing to provide funds.

Helping the kids cut their budgets and restricting how much money they'll provide for some, if not all, expenses will be a help in the long run.

Otherwise, parents could end up dependent on those grown kids once they retire—and if the kids haven't learned to live within their means, that could leave the parents out in the cold.