There isn’t a specific minimum score that you must have to get approved for a mortgage. Your credit score is just one factor that lenders use when deciding if, or how much, to lend to you. There are also various loan types, which have different minimum scores, as well. An FHA Loan, for example, requires a FICO score of 580 and a down payment of 3.5%. But, you could still qualify with a score lower than 580 as long as your down payment is 10%.
Lenders also have their own thresholds for lending. As an example, while you may be approved by a lender with a lower score, you are likely to get a better interest rate if your score is high enough. And, as with the example of an FHA Loan, you might be required to have a higher down payment.
Your potential lender should be ready and willing to provide this information to you and explain in detail all of the lending criteria.