I rescued a patterdale cross 18 months ago and to this day, everyday is a battle. He has seperation anxiety and has to be right beside you if not touching you at all times; he is incredibly greedy so will eat literally anything including his own poo; and hates all other animals to the point where we cannot ever let him off lead unless the space is 110% enclosed, else he would massacre those animals. He is very strong, a ridiculously powerful dog who can pull over even the tallest, strongest men I know on walks if they're not expecting it. For a 7kg 1ft tall dog, he can jump a good metre or so in the air without any warning or running, just straight up in the air. He doesn't always understand when playtime has finished and you have to shut him away to calm down or he gets very nippy. When he is told off for anything, often his first reaction is to find somewhere hidden to wee or poo. He often seems to have no concept of loyalty beyond who has food at the time. He is difficult to train, takes a lengthy time to teach him anything and comes off as being dormous (our nickname for him is dormouse.) As you can imagine, he has a lot of issues. BUT. He is my bestest friend in the world. He can be incredibly clever and he knows when he's doing something either good or naughty. He's the best guard dog we could ask for - barking at every strange noise or intruder-sounding sound. He tells us when he needs a wee, or a drink, or most commonly, breakfast. He trusts me enough to let me pick him up and cuddle him, and more recently, even touch his paws which he used to HATE, for a reason we will sadly never know. He'll take food from my mouth as gently as possible. Every dog is different. Every terrier is a potential nightmare. Every patterdale is a character that I can guarantee once you get to know, despite all his faults, you will fall so madly in love with him, that you'll take all the nips and the inside wees and the barking and jumping up and the hell that having a rescued terrier can sometimes be. There is a hell of a lot to consider. Before you set your heart on it, think seriously about how much you will need to put into rehoming and raising a dog with typical terrier traits and a difficult backstory, you may need to sacrifice a LOT for this little guy and you have to be prepared to stick with it, and slowly work through the issues. Don't go into this lightly because he will fall for you as his new owner, and if you can't handle the pressure of a difficult rescue dog and send him back to the kennels, you'd be breaking his heart all over again. Good luck in getting a new dog; don't be put off by mine because he is an extreme case, but be cautious :)