Financial talk

I'm a rather THIN Chick if u ask me...I'm 130LBS and 5'6 I would like to loose some of the fat around my mid-section!! I do at least 30 sit-ups 3 times a week..i know pathetic right !! But what will i have to do to get a FLATTER stomach w/o buying some type of exercise equipment or going to a gym...Money's Tight rite Now LOLz!! Any answer/tip/help is welcomed!!