Are there definite rules about exterior doors opening inward, or outward?

Not common, the customers preference wins.

Inswing doors are amenable to the addition of a screen door; out-swing doors not really so.

I always try to steer clients away from screen doors. A door is meant for ingress and egress and a second door makes it far more inconvenient for those purposes. A well-designed space should have adequate windows (with screens) for good cross-ventilation.

Additionally, insulated doors with vinyl light dividers have been known to melt from solar heat when a storm door is added.

Are outswing doors common? or Are interior screen doors common?....either way

You could use a retractable screen. No egress issues when the main egress door is closed and the screen is hidden away and you will not have the usualness of an interior screen door. When the main door is open - close the screen to enjoy the outdoors. Not much more expensive than a good high quality wooden screen door - We typically pay about $275 including install.

There are many manufacturers these days - Phantom was one of the first and we have had good luck with them - www.phantomscreens.com

I actually specify them on most of my remodels, additions & door replacements for a few reasons. During high wind events this will actually help keep the doors sealed up, they are more secure / can't be kicked in, and they leave more room inside the house.

I would worry about what happens to the the outswing door standing open and the wind picking up. Will it constantly slam shut? Or will there be troublesome loads/forces on the hinges as it's blown against the casing etc? Potential damage to the hardware etc. Just things to discuss with your client.

Outswing is a new local code requirement in hurricane-prone areas.

More Secure?

When the door swings outward, the hinge pins are typically exposed on the outside of the house.
This could allow an intruder to tap the hinge pins up and out, and lift the door off its hinges, removing the door without unlocking it.
There are several door hinge designs available that make it more difficult to remove the hinge pins.

You never see outswinging doors in Vermont

Absolute statements are, most often, absolutely wrong.

I've specified and installed outswing entry doors in Vermont. It's often easier to find a low-profile, wheelchair-accessible sill in an outswing door and they close against their weatherstrips when the wind blows, making them more air-tight.

As long as they swing out onto a protected entryway, snow buildup should not be a common problem.

And, John, entry doors typically have fixed hinge pins, and outswing doors always so.

We use outswing doors all the time - mostly on covered porches. Remember to upgrade to the stainless steel hinges when you use them - you would think this would be standard but it is not, even for some of the upper end door companies.

You can get a much higher DP rating on an outswing door.