If you do this after you’re under contract to buy a home, you’re probably not going to get the loan. If you do it far enough in advance (as in 3 or 4 months), the lender will just see cash in your checking account and a certain amount of credit card debt. If the debt isn’t too high, they will probably remain blissfully ignorant of where the money in your bank account came from and approve you for the loan. Again, if you’re doing this, talk it through with a good mortgage loan officer before you do it.