Currently have 2 doors rented and 3rd we currently live in and made significant improvements to and will rent out in the next year or two when we move out. Also have 100 acres of land in forest management program that pays $ to offset property taxes, and a small gravel pit that pays out some $ each year. We use YNAB to track spending and all rental related info is dumped into its own category. Then I put that into google sheets for breakdown income/expenses other info. Use google drive for storing PDFs and other relevant info.
We setup Cozy for screening and also ACH rent payments for the first time and like it so far. There is an expense tracking section I have not looked at much yet.
I would probably wait until 4-5+ doors to use a specific program, and who knows if we will actually get to that point. Unlikely we will find properties in our town to buy, and would have to go to neighbors towns about a 45 minute drive away where some do look promising. If so, I would probably use QuickBooks online since I am already familiar with it. Could use classes to categorize expenses by properties on the P&L. At that point I would probably quit YNAB and just use another class for personal expenses. But I work in QB quite a bit, so there wouldn't be a learning curve at all.