Mountain of Fire by Jo Grafford

How to convince a woman you just met that a marriage of convenience is the next best step…
Wayne Whitaker (or Chief Lighthorse, as his tribe calls him) is constantly putting out fires on his poverty-stricken, crime-ridden reservation. Many of the old-timers on his council fear it’s because he’s too young, too inexperienced, and too single to run both the tribe and his family’s rodeo business.
While assisting a lovely seamstress on the side of the road, it’s not love at first sight for Wayne. He’s too old for stuff like that. But it’s the beginning of something special that he’s convinced could turn into more.
When he discovers the single mother and her son have fallen on hard times, he sees the perfect opportunity for them to help each other out. He’s as surprised as she is when she says yes to his impromptu marriage proposal. Does it mean she feels a spark of attraction in return? Or will his growing feelings for her end up being yet another fire he’ll have to put out?