Make Believe Fiance (Make-Believe #2) by Vivi Holt

Set in Billings, MT. Gwen is a down on her luck, divorced waitress/3rd grade teacher and Heath is an extremely wealthy acting CEO of a ranching corporation. So when Heath is ready to take over as CEO (no acting) he realizes the fact that he's not married might be holding him back and asks Gwen to be his fake fiance in exchange for paying her first month's rent on a new apartment as she has just been evicted.