What are my chances of getting approved for a mortgage if I have no credit score?

What are my chances of getting approved for a mortgage if I have no credit score?
Added (1). I'm 20 years old and my landlord just told me she's listed my home on the market, but she told me if I wanted to keep my house I'd have to re-finance it through a mortgage. I'm the only one of my roommates that has good credit an that's because… I don't have a credit score. Could I be approved with a co-signer? If not what should I do.

P.S. I should mention that my landlord said a land contract is not an option.

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