In the same town, I have a client who had a competitor that went out of business a few months ago.

The competitor's defunct website is still ranking higher than the client's website in search results for the same keywords.

The client wanted to try to purchase their competitor's domain name and just use a 301 redirect to point to their website.

The competitor's domain name is splashed all over the place--on social media and legitimate directory pages (like yelp and a few locally-driven business listings).

Is this a legitimate technique, or will it hurt rankings in the long run?