So in many jurisdictions the city doesn’t actually take the properties. Instead they auction off a lien to a private company/individual and then that individual can foreclose if the tax isn’t paid. So this strategy might not work.
So you buy from the private company after they foreclose.
At that point the title is clean, so I would expect the property to sell much closer to the market rate minus any repairs needed to make it livable. Not really a deal to be had.