Has anyone acquired a site/app/business mainly for their audience or SEO reach? What's a good marketplace to look for these opportunities and any tips on treading these waters?
I purchased a site on Flippa back in 2015 with great SEO and it worked out well as I was able to migrate a lot of the traffic. But the quality of available sites on Flippa has gone down a lot since then.
What I would suggest is doing a google search under your preferred keywords and see if it brings up some inactive sites, and then reach out to the owners directly about a sale. I've done this in the past with some success. It can be a bit of work, and a lot of hit and miss to find the right one.
Good tip on reaching out to inactive sites! When you purchased those sites, did you keep running them independently and just create more content/links from that site to your main site?
That's what I did, I found it was important to keep them running and preserve the link juice.