I made a HUGE mistake buying expired domains for SEO

CRAP! Recently I've been buying a lot of new sites and expired domains with high domain authority. I'm not trying to build a spammy PBN; I plan to build them up as really good content sites and also use the backlinks to strengthen my main sites. But I made a huge mistake.

Firstly, I bought some that were a bit spammy. I didn't think that was a big deal. I was too focused on high DA and looking for 60/70+ authority sites. I did check the backlinks and tried to find ones with really good authority backlinks. But I didn't look closely enough.

I'm glad I paid for DomCop because it's the only tool that gives me a little orange "this site has been flagged as spam" arrow.

But that's not enough!

I thought I could redo the sites and that it wouldn't be too hard to remove the flag, since I don't plan to have spammy content. One of the sites we bought and set up... we can't get Google to approve. We've requested and been rejected about 5 times already. So that's a big problem, apparently this is much harder than I thought, to redeem a spammy site and get Google to list it again.

I might move the entire site to a new domain (even though, apparently, Google can track the content and block that site too).
I found another similar domain that looks great and is getting traffic - hurray!

But checking with domcop, I realized it has a spam flag too... even though it's still listed in Google! They just haven't banned it yet, but they still could. And unfortunately (I mean shit!) another site I had bought that I've already got half built with content, is not listed in Google.

This is the huge mistake: before buying any site, google the domain name and see if it shows up in Google. It wasn't clear to me previously that this particular site will NOT be listed, so no amount of good new content will save it. It's so stupid, and so easy, I'm pissed at myself for not realizing this until after I had spent thousands of dollars. 

Spammy links or a flag warning are OK as long as the site hasn't already been blacklisted from Google, because if it has, it's very hard to earn that trust back!