My brother-in-law is temp. living with his brother & I (his brother's wife). He is afraid to live alone. Has mental issues that he is seeking counseling for as well as being medicated for. His wife of 45 yrs. did everything, bills, checking, as well as keeping him from coming & going in his later years by refusing him a key or code to sec. system. I fear for him to be alone just from what I've seen & will share this with his psychiatrist. Do these things qualify him for assisted living? He has an insurance policy in case he ever become unable to live alone for medical reasons. Do you accept this type of insurance?
Bottom line, you don't need a drs referral, if your brother has the money and/or insurance for long term care, he can become a resident. He will still need relevant medical information for review and as a condition of his being accepted as a resident.
Visit a few and read the fine print to understand all that is included, ala carte care costs, security, available medical services, etc. make sure the facility is appropriate for your BIL's needs.