First, hello!! new member here. I have tried to search the web for the answer but apparently I don't know the correct terms to search for... SO I'm hoping so real people can help. As the title suggests, I am looking for a business theory or idea, something I can look into more and/or some kind of general formula I can apply day to day. Example: Lets say I have a thing. And with 1 hour of work and nothing else invested I can sell that thing for $150. Now lets say I have that same thing, and with a $30 investment, 1 week delay, and 4 hours of work, I can then sell it for $250. I am looking for the theory and/or calculation to help me determine if of if not I should invest the $30 & extra time. PLEASE know that this is just a simple example. I do the work (but I will apply it to other works as well), the items, initial costs, investment costs, time I could invest into the project, etc.. they vary project by project so no one single answer would be correct. That is why I am looking to study up on whatever this is called. I sure hope I made myself clear. And thanks.