Why grind for the money when you can give yourself however much you want on day 1? It's very simple, honestly. I mean, if you want to get the authentic experience by having to fuck around with stonks and all the other ways to get money, I say to each their own.
Say you start a new game, and you make a save as soon as you get the first chance, while it's day 1. Minimize or leave the game, then go to the save file location (...Users/[your profile]/AppData/LocalLow/IncontinentCell/My Dystopian Robot Girlfriend/Saves), and scroll down to the bottom of the list of files.
Your save files will look like this: M1.mdrgslot -> Save slot 1
Open the file using a text editor like Notepad++, then search for "money" and it'll take you to the field you need to edit. Give yourself as much money as you want. I started with 73 million, just for shits and giggles.