How do you get a limo license?

Well, that depends on your state. There is no such thing as a "limo license", and a CDL is only required for for-hire vehicles which transport more than 15 persons (including the driver).

In a lot of states, no additional licencing requirements are imposed for the operation of vehicles which do not fall under jurisdiction of the FMCSA (heavy duty trucks, buses, vehicles hauling hazardous materials). Thus, depending on your state, you might just use your standard drivers licence. Other states may have a "chauffeur's licence" system for taxis, limos, vans hauling up to 15 persons (again, including the driver), etc. This may be achieved if you find a limo company willing to do on-the-job training, or through a driving school which offers such a programme.