I want to set an account up for my gfs kid with a little bit of money for stocks so they can watch it grow and have a little bit of money saved up for a house or something when its time.

Is there a way I can set it up so both child and mom have to be present to take the money out? I trust mom to leave the money for the kid to have fun with (and save for smart spending) but I am pretty sure as soon as dad finds out about the money it would be gone.

This is just a little bit of money for fun. Not worried about any of the issues involving the relationship.

How about a joint investing account or a TOD account?

You shouldn't have to worry about a tax issue whenever you want to straight up give it to the kid until it hits $10k.

In the meantime it's yours, legally.

Set up a trust.  Make the kid the beneficiary and yourself the trustee.  At a certain age have the kid set to become the trustee and beneficiary.

There are better choices if you are specifically saving for college but based on what you describe a UGMA account might be a good choice.  It becomes the kid's money legally when you deposit it and they gain control over the account when they turn 18.

I don't have intimate knowledge of the rules but there are limitations in place on when a deadbeat parent could (legally) raid the account.  If mom is the custodian and the kid is the beneficiary then I don't think dad would have any access to it but I'm not qualified to tell you that for certain.

The downside is that if the kid is raised wrong they could always turn 18 and then waste it on hookers and blow.  My grandparents set up such accounts for me and my two sisters though and we all did the right thing when we turned 18 and kept the money invested or used it as a down payment on a house.

You should open a UGMA/UTMA. Easiest option for everyone. The kid's mommy can be listed as custodian, or responsible person in charge of handling the account until the child reaches the age of majority in the state the account would be established. The child doesn't need to have knowledge of the account until the child reaches the age of termination. The assets within the account would then have to be legally converted into an account in the child's name. It can also be converted into a joint account with the child and the mother, so she can still have authority over the assets if the kid is an irresponsible piece of..... No one who is not listed as custodian, i.e. deadbeat parent, would have any legal ability to seize the assets in the account. The assets belong to the child. Investments can be treated or transacted in the same way any other brokerage account can be used. Trusts would be overly complicated for this situation. The child is not yours, and the child's mother is not your wife. That is not something you want to go into. As always, you should seek the advice of a qualified professional......