Happily will meet you in advance to get to know you and your dog to make sure you’re comfortable for me to look after them. I've been around animals (both dog and cats) my whole life and my parent currently has a 5 year old border collie. I mentally stimulate our dog by playing with him, using his brain with the classic “find it” game, whilst physically stimulating through walks (runs for him) and lots of stick throwing! We had 2 dogs growing up that sadly passed away, one of which was a rescue dog and so I understand how you may need to act differently to make the dog feel comfortable. Ive also got experience with reactive dogs. I understand that there may be triggers so we’d discuss in advance what those triggers may be to ensure any reactions are properly managed for safety of your pet plus anyone or anything nearby. I’ve looked after many dogs ad-hoc including Manchester terriers, beagles and Schnoodles. For these occasions, I’ve stayed at the owners house and kept the house respectable. All of which felt easy in comparison to looking after a border collie! By the end of the day, the dogs are often asleep on my lap (or I sit on the floor with them if the owner doesn’t want their pet to be on furniture!), fed and happy.