I'm a sucker for strays,
just watch him closely and don't trust him with anything dear to you, my sister took in a white shepherd stray, now that we think about it she had probably been dropped off and was running with some of the packs around there, after she made herself comfortable she took to a meal of horse rump chasing all the miniature horses luckily my stallion was out and he took care of the problem, she's indoor/outdoor now (penned only) we could never get rid of her and didn't want to send her to a shelter.
This dog was also very sweet and timid, but she just one day decided to take off after them, she'd chase down anything she could get.