The Newcomer by Mary Kay Andrews

 Letty's sister Tanya's decision to get involved with a sketchy rich dude named Evan was the worst mistake of her life. It ends up with Tanya dead and Letty fleeing to Florida with Tanya's young daughter, Maya. Letty and Maya land at a motel near the beach, based on a "clue" that Tanya left. Ava, the kind-hearted owner, takes them in, giving Letty a job and a place to live. But the owner's son, Joe, is a cop, and he is suspicious about what Letty and Maya are really doing in Florida.

The Newcomer is a love story and a thriller--as 2 bad guys from Tanya's past are seeking Letty and Maya along with a missing fortune. Good story, good characters