Expansion can be done succesfully, but you need to be prepared. Just look at other companies with multiple locations. Do you have enough capital to open a branch and sustain it until it becomes profitable ? This could take two years. You have to research the new market to see if it will support another firm.
Like Mustang stated you need controls and procedures in place for every detail of the business.
A training program to teach new hires the right way of doing things and how to follow your plan.
A manager to either handle your existing business or to run the new one.
You will need to spend time at both locations - can that be done efficiently from Rocky Point or Islip or whatever your location is ?
It takes capital, planning and risk.