Get your license.
Actually, the proper FAA term is a private pilot certificate, and the kind you'll want is called "Aircraft, single engine, land," or PP-ASEL. In order to earn it, you'll need a medical checkup, then spend a minimum of 35 hours ground instruction and 40 hours in the air, followed by a written test, an oral test, and a check ride with an FAA-designated examiner. Realistically, you should expect to spend at least 60 to 70 hours of flying time before trying to pass a check ride, a process that will cost you on the order of $8,000. Doing all that can take anywhere from a few months to a few years, depending on how aggressively you pursue your goal. Once you get your ticket, you're legally qualified to fly at night and with any number of passengers, though you can't fly inside clouds – you'll need additional "Instrument Flight Rules" training for that, which will cost about the same amount of money again.