1, your brother "made a loan with your real estate license", that is, he made a loan with your real estate as collateral. If your brother mortgages your property, you must get your written consent, that is, you are willing to mortgage your property. If your brother can't repay the loan in time after your property is mortgaged, the bank can auction your property to repay the loan. If you and your brother want to write an agreement, the key point is that if your property is auctioned because your brother can't repay in time, your brother should bear the responsibility.