What part of analyzing a rental deal still takes the most work?

I’ve been diving into how people go from crunching the numbers on a rental property to feeling comfortable enough to make a deal.

What I've noticed is that getting those initial numbers is just the tip of the iceberg. There's still a lot to double-check before you know if your assumptions hold up.

For those who frequently analyze rental properties, what part of that process takes the most time or effort for you?

I’m curious about a few things:

1. What numbers do you find hardest to get comfortable with?

2. Are there things you still need to manually check, even if you're using a spreadsheet, calculator, or paid tool?

3. What do you do when you get different numbers from different sources for things like rent, taxes, insurance, or comps?

4. Have you ever found something out that was significant enough to make you lower your offer, renegotiate, or just walk away?

I'm not asking for the perfect process, just what you actually do now and which parts can still feel like a headache.