📈 Calculate Return on an Investment

I approve purchases without any real idea whether they pay back. Build me a return on investment calculator. Let me enter the one-off cost, the ongoing monthly cost, the expected monthly benefit whether that is money saved or money earned, and the period I care about. Work out total cost, total benefit, net return, return as a percentage, the payback period in months and the break-even month. Keep every assumption as its own visible, editable field with a note explaining where the figure came from. Let me save each case and compare several side by side. Add an AI agent that takes a case, rebuilds it on deliberately pessimistic assumptions, and tells me plainly whether the decision still holds and which single assumption the whole case depends on. Automate a scheduled reminder six months after a decision to come back and compare the forecast against what actually happened. Two logins: an analyst who builds cases, and an owner who approves them.