I would say it depends on the size of the site, if it's a large site, you can be wasting Google's crawl capacity by having it spend time following 301 redirects from nonexistent pages.
Google does a pretty good job explaining the soft 404 conundrum:
Returning a code other than 404 or 410 for a non-existent page (or redirecting users to another page, such as the homepage, instead of returning a 404) can be problematic. Firstly, it tells search engines that there’s a real page at that URL. As a result, that URL may be crawled and its content indexed. Because of the time Googlebot spends on non-existent pages, your unique URLs may not be discovered as quickly or visited as frequently and your site’s crawl coverage may be impacted (also, you probably don’t want your site to rank well for the search query [File not found]).
We recommend that you always return a 404 (Not found) or a 410 (Gone) response code in response to a request for a non-existing page. You can improve the user experience by configuring your site to display a custom 404 page when returning a 404 response code. For example, you could create a page containing a list of your most popular pages, or a link to your home page, or a feedback link. But it’s important to remember that it’s not enough to just create a page that displays a 404 message. You also need to return the correct 404 or 410 HTTP response code.
Here's the thing, if you keep it as a 301 redirect from the old listing page to the property overview page, that old listing page will stay in the search index longer since you're not showing a true 404 response code. So if people are in the search results and click on that listing there's two ways of looking at it: if they click on the non-existent listing, well at least you'll still be driving a little bit of traffic to your site and hope they look at other properties. On the flip side it's a poor user experience since they were expecting to see that property page when they clicked from the search results, but instead are just being led to another page.
I think the decision lies in the size of the site. If it's a huge site, let them hard 404 and follow the best practices. If it's a small site and you're hoping people stick around serendipitously, you can probably keep doing what you're doing.