Don't buy streams from people, they are for the most part going to run ok bots with awful proxies to max out their own profits. They also use free accounts lot of the time and this will get you flagged for ad fraud which they go harder to protect. You have to run your own bots or find someone who can build you custom bots to run for your farm that uses for only premium accounts so that you can avoid detection. This isn't fool proof after all sometimes you just get unlucky, but most people make the mistake when starting out to buy streams.