i am pretty open as long as he was around her age (or at least college aged) but if you want pb suggestions i can give them!
and i love the sound of him. i'm thinking they were basically strangers at first and it was a relationship that developed over time. and if you wanted he could have the substance abuse issues and we could even just nix the affair part? i could see it being an issue for her especially because she expects things to be perfect and if he was not filling that role there would have likely been many fights.