You’ll go broke if you wait for sick patients to walk through the door. There aren’t enough of them to go around. Consider doing wellness medicine, which widens the scope of potential patients to include everyone.
Develop a sub-specialty such as in dermatology, thyroid disorders, diabetes, or geriatrics. Get into occupational health — pre-employment physicals, drivers’ physicals, flight physicals, workers’ compensation for minor injuries, drug screening, etc — and advertise that you offer these services. A river of money may run by lawyers, but it doesn’t run by physicians. We have only rivulets, but add them up and you will have a mighty stream.