My net cash flow is plenty (16k/month) so I can afford to replace a 7k HVAC or 9k roof if necessary.

I'm not aware of any way to replace that metric with STR income.

Do not must patch the roof, REPLACE IT, do not just " tune up" the furnace replace it etc.

Or you can use the proceeds to purchase two replacement properties. 

You both make 100k a year and you want to build a 4-plex to replace your job and only manage the property or cruise off passive income?

Cost to replace.

Roof replacement - maintenance?

They will make cheap/easy fixes or they will discover your specific problem isn't covered by the warranty and you'll have to pay for repair/replacement anyway.Most property managers will not manage a home with a warranty because of the rejections, delays, and poor work. 

The resort plus condo fees and replacement fees keeps nearly 66% of room revenue.

Ambitious engineers and product managers sometimes see a stint in Big Tech as a way to gain the experience and financial cushion that will help them create their own startups.