I have two Duplexes that I use Cozy and Stessa to manage.
Cozy is great for collecting rent, running background checks, and handling maintenance requests.
Stessa is very similar to Mint.com, but geared towards Buy and Hold RE. Before Stessa I was using XLS, and this worked well, but for the level of detail I want, took a decent amount of time to manage each month.
Stessa helps automate all this. I linked it up to my Landlord Credit Card and Checking Account, and for the most part it works great. I see the charges come through, and categorize them as I do. Then at the end of the month, I do a "status" check self review to make sure everything is in order. Then, for Tax Season, it has a good export feature to export your Income Statement, Cashflow Report, Transactions, and receipts. (I really like the feature of adding receipts to transactions.
Overall, it's a great tool. However, it does have some issues. For example, I linked it to my Capital One account. I need to re-link my Capital One account each time for the transactions to download, which is a pain. I asked Stessa Support what bank they recommend (one that works well with Stessa), and they literally could not recommend one... so I'm not sure what to make of that.
I'm speculating, but I don't think I'd use it for more than say 7 properties. My goals is to continue to acquire properties (40 doors in the next 4 years), and I expect I'll ultimately need to upgrade to Quickbooks.