Are straightners gud for hair?hlp me............................…

i have an idea of getting a straigtner but this is my first time.my hair looks dry and weak.i would lik to use straightner is it gud to get a own or i have to go for parlour to straigten my hair.if i own one how many times shud i straighten my hair.plz let me know the best brand of it..my frnds are suggesting me not to use as there is a risk in losing hair...plz help me out!!!!!!!!!!!!