Yes, if you take a first class medical, it is good for first class privileges for the time duration (6 month or one year according to your age) then unless you are flying where a first class is required, you can continue to fly under second class rules until that time period expires. If you are then not flying for hire yet, you can continue to use it as a third class until the time frame for third class expires. Good luck and remember that flying is suppose to be fun. I flew pipeline inspection four years and built over 7000 hours of flight time and was paid well. Flying is one of the only jobs that I can honestly say that I looked forward to getting up everyday for work.