<prompt> Human: Hi PF,This post is for my best friend who recently got a job in sales and got a commission check of 30,000 in her first quarter. She likely wont get anywhere near this amount again. Ive learned a lot on this sub, so my first advice to her was to set up an emergency fund 6 months living expenses which is about 10,000 on a tight budget. Shes going to take another 5,000 for a fun fund which will cover vacations and other events she may want to participate in the future.This leaves 15,000. Her mom is about that much in credit card debt and has cancer, so her main concern is if that debt were to fall on her she wants to pay it off now. Based on research, since she did not cosign, it would go to the estate which would declare bankruptcy theres no inheritance there so she shouldnt need to.My thoughts on the 15,000 are to put it in index funds: 70 - VTI 30 - VEUNow, my question is, should she put this entire 15,000 in at once or Dollar Cost Average it in? The market is at an all time high, and no one knows where it will go from here. My thought process was to Dollar Cost Average it in, and if theres a dip at any point, buy extra shares on sale when it dips.Would it be better to just put the entire lump sum in at once or Dollar Cost Average?Thank you!Edit: formatting  <response>: my question is, should she put this entire 15,000 in at once or Dollar Cost Average it in?Time in the market is always greater than trying to time the market. If this is a long term investment then put it in and let time do its thing. If this is a shorter term investment and she might need some of the money sooner, then you could make an argument that DCA might be better. 