I had the man fairly young to begin with, maybe about 30 years old. So not a "dirty old man takes advantage of a young girl" story. But I probably ought to get her to 18 before any serious sparks fly.
Wife was spoiled and used to higher standard of living so went back to her wealthy parents and filed for divorce taking the baby with her. Husband a decent guy but not very ambitious and the wife wanted more. Once she leaves, the man gets depressed, spiraling downward, on verge of losing his job and drinking too much. He's a mess and so is his house. Then this "runaway" teen enters the scene and eventually gets this guy's life back on track after he takes her in and allows her to get her life in order. This is a very intelligent and strong woman with good Christian values who was simply fleeing a bad situation at home. So the guy saving himself by saving her becomes the main theme here. Maybe I'll build in a subplot where the guy goes into business for himself and his venture really takes off making him wealthy. All of this of course, making the ex-wife who dumped him for being a loser sorry she left him in the first place. Maybe I'll find a way to get the kid back to him as well.
Anyway, I think it's the basis of a pretty good story. I'm sure this type of story has been done before but if I am able to finish it, I'll make sure it has some unique twists.
I’d think a little more about the son aspect. Just me talking, I think reconciliation of a father son divide has appeal and it deals effectively with the age gap issue.
Just me talking. Whatever you decide to do will be workable and entertaining.. Looking forward to it.