Pay off collections OR Wait it out?

I have 5 or 6 collections accounts on my credit report that should drop off in 2018. My credit is currently 606. I was told that in order to qualify for a mortgage, I can't have anything in collections. I was also told that if I pay off my collections, my credit score will actually drop. So do I pay off my collections and drop my score? Or do I not pay anything and hope my debts don't get sold again and drop off? Meanwhile I'm paying 1,100/month in rent and dying b/c a mortgage would be less:)

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