What is birth control?it is 100% safe?me and my gf want to have unprotected sx.after taking birth..PLEASE HELP?

My gf will not able to produce baby after birth control??howmuch its cost???we dont want to take any chance of pregnancy..we both are studying nw.and want to have unprotected sx. according to u,,which is the best idea to prevent pregnancy????condoms and birth control???which one would be better???any problem in future after taking a birth control???????