Three Months and You're Mine — Casey McMillin

This fifth and final book of the In Too Deep series can be read as a stand alone romance. Meredith Blake had a plan. She was moving to Los Angeles to make it in show business and thought she needed someone to teach her the ways of seduction to help her achieve that goal. Even though she had already chosen her teacher, there was a problem. The guy was her big brother's best friend and he knew better than to have casual sex with her. Zack Larson, US Olympic swimmer and all-around good guy, was too smart to go messing around with his best friend's little sister. He wasn't opposed to one night stands, but it was an unspoken rule that little sisters were off limits. She was four years younger than him and he'd always thought of her as a kid. Plus, as the hot one on the swim team, he had too many girls on his plate already. Meredith knew her plan was fool-proof and was prepared to stop at nothing to convince Zack to help her out. He agreed under one condition, that they wait three months before sealing the deal. He assumed she would forget about it by then, but that just showed how little he knew about Meredith and the feelings he'd have for her.