Leo,
Coyotes are rather thin skinned and don't require Magnum type handguns to bring them down. They can be quite tenacious though. When it comes to trying to nail a coyote with a handgun, I would suggest something that does not have a lot of recoil. Besides, if your trying to grab reins or horn and shoot at the same time, things can get Western!
A Glock, M&P, or 1911 in 9mm would be a good choice in your friend's circumstances. Shooting a standard defensive type JHP that will rapidly expand will do the job nicely. The 9mm practice ammo is also something that they can afford more readily, and guns are plentiful. Used police trade in guns are common too.
They also don't have to be "into guns". Just a few practice sessions for familiarity can get them going.
Plus the plastic guns work well from the utility perspective of the dirt, sweat, hair and grime that comes with being around hay burners. They can take a lot of abuse and still go bang when needed.
