Many loans don't require a minimum number of credit lines (aka "tradelines"). Your mortgage broker should tell you if the loan you are considering does have a tradeline requirement. Even if there is a requirement, there are many ways to quickly build tradelines depending on when you're planning to secure financing. For example: your spouse can apply for a couple of credit cards or you can also add them as an authorized user to some of your accounts, which might help improve their credit profile as well.