and is 18 to late to start voice lessons, i play guitar and now want to began writing a singing my own songs.
You don’t have to be born with it. Some people are. Then we have the people who took voice lessons. Also, remember that you are never too old to do anything. Especially if you want to follow your dream. If singing is your passion and something you want to do the rest of your life, take voice lessons and you’ll find that you have a great voice. I believe that you will go far 
I wish you the best of luck