To dredge up an old issue from this thread, and as a caution to all those building private courses:
Course directories.
Our course is only open if one of the owners are home, and only by advance reservation.
We've listed it on DGCR, PDGA, and it's on UDisc. Each of those includes a warning that it requires reservation, and people mostly comply---other than a few with apparent reading difficulties, or remarkable laziness. As a backup, we put a large, tactfully-worded sign at the start of our driveway, tactfully saying 'No trespassing unless you have a reservation", to stop those who get that far without calling first.
But.
There are other course directories, some of which seem to just scrape info from the PDGA or elsewhere, which don't include the private course disclaimer. Astonishingly, there are people relying on these instead of the more comprehensive, better established ones.
Some I can correct. Google Maps put our course in as a business; I was able to update it. Someone originally entered our course into UDisc, and the UDisc folks were friendly and at our request, added the warning. Others, however, are impossible to contact.
So a couple showed up at our driveway this past weekend, using a phone app I'd never heard of. Luckily for me, they were conscientious, retreated down the road, found our number, and called. Luckily for them, I was home and could accommodate them on short notice. (I also put them on the right track, telling them to check out DGCR instead).
But I can't find any way to contact that app maker, short of buying the app.
So here's the caution for private course owners: Once you list a course anywhere, the listing will spread to places where it won't be accurate, and can never be stamped out. I'm not saying you shouldn't do it. I'm certainly glad we did. But just know what you're getting into, when you do.