Hey Nick!
For actually setting a limit on number of tickets available for an event, it seems like the default “Ticket Stock” option would work great for this. Here’s a screenshot of what I’m referring to, just to be 100% clear → https://cloudup.com/cKOb4GTVzGB
Now, as for displaying a message when the ticket stock is low, that would unfortunately require some custom code. We don’t offer support for custom code, technically, but I do have some code that you can use for reference here → https://gist.github.com/ggwicz/e4d0d46cdf6d3977e5bc#file-ticket-stock-example-php
When you use that function, as it stands right now it will just display the ticket stock numbers on the front-end of your site. But notice the $ticket->stock variable down at the end of line 27 in that file?
Well, if you simply add some extra code here that displays a message when it is less than nor equal to 5 (i.e. when only 5 or fewer tickets remain…), then you should be good to go here. Something like:
if ( $ticket->stock && 5 <= $ticket->stock ) {
printf( 'Only %s tickets remain, book now!', $ticket->stock );
}
I hope that helps, cheers!
— George