You do WH SEO ? People link to your site, cos it so cool and funky ? You don’t buy / exchange links ? Ask yourself R pure WH ?, otherwise You hat is in a shade of gray 
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I used to do both BH and GH seo. I know expired domains business is lame. The cost of good expired domain is >400$ + links + content … you need to keep your fingers crossed, it would not be banned from G in 1-2 weeks time. For some small kw domain can stay a bit longer, but it’s like a lotery .
Take a look at pharmacy kw like viagra, tramadol, fioricet …. tons of BH SEO.