Mistakes, lessons learned.

Worst case, hard money may be an (expensive, short term) option.

Lessons learned and mistakes made during this deal are certainly long lasting and impressionable.

I've never heard of anyone requiring this, so it seems strange to me.You hate to think the worst of someone, but since they just bought the place, I can imagine they have a home inspection report full of little things that need fixing, and I worry that they're trying to pass the cost on to me.

You are making a classic (short-sided) mistake of just seeing the income, while not seeing the value. 5% vacancy on the revenue of $100,000 per month adds up to $60,000 - this is what I am creating/saving.

Make sure you have back up funds encase the worst happens.

When things are looking absolutely fabulous and prices are going wild is the worst time to invest. 

I'm usually quick to act, especially with my background in flipping, because I know deals can go quick but I made the mistake of thinking that because it had been on the market a while, I had time (just like you said).

One small mistake can cost you a fortune.

The worst that could happen is the tenant refuses to pay, you end up in court, and the judge throws out your claim for some obscure reason or because he doesn't have enough fiber in his life.