Inspired by some of the "lessons it took me years to learn" threads floating around today, I am curious specifically about the financial and bookkeeping side of things, because I think that's where some of the most expensive mistakes happen quietly. Mine was treating my portfolio like one business instead of several. For the first couple of years I had a decent sense of total cash flow but what I felt like was missing was visibility into which specific properties were actually performing and which ones were quietly dragging the average down. I found out the hard way when I went to refinance one and couldn't produce clean financials for it without a significant amount of manual work.  From that point on I treated every property as its own entity financially: separate tracking, separate P&L, expenses categorized at the property level in real time. Not just sorted out at the end of the year. It changed how I made decisions about which properties to hold, which to sell, and where to put the next dollar. What's the financial mistake you made early on? Could be bookkeeping, tracking, tax prep that you wish someone had told you to avoid?