SPOILERS - SECRET ENDING GUIDE. I recommend you try getting them yourself first, using hints dropped by a comment below. This will go into a lot of detail and is for if you just can’t figure it out.
1.) Immediately start spending money.
2.) Pay for the border wall and then don’t built it.
3.) Pick “What else?”
4.) Fund NASA.
5.) Double every Amazon employee’s salary.
6.) Buy Twitter.
7.) Show your nibling Twitter.
8.) By now, you should have $200 million left. Fund the animal rescues to get your value to 0.
9.) This will lead you to a secret room from which all the secret endings branch off of.