Will neighbor's dog lift his leg in our house?

You may want to bring him in briefly, watch carefully and if he begins to try to mark territory, take him out immediately. If Zack is an unneutered male there are good chances that he will try to lift his leg, also, does he do this in your back yard?

How the hell should we know? Females mark just like males so being male doesn't mean he will automatically cock his leg and mark in your home. Did it not occur to you to ASK THIS before you agreed to watch the dog? If its such a concern pick up the phone call the number he left with you and ask.

ETA: Fixed males can mark and just because he marks outside which is perfectly acceptable does not mean he will do it inside.

ETA: pointing out your lack of common sense does not make me a "hater"

Hater - "A person that simply cannot be happy for another person's success." Excuse me but none of the above fits the definition of a hater. This is a situation simply solved by asking the dog's owner what their dog is like. If they have a brain then they have trained the dog NOT to mark inside the house. simple. Instead you come online asking people who know NOTHING about the dog to make an ASSUMPTION about what the dog will or won't do.

If you are going to try and insult or label someone it helps to know the DEFINITION of the word or phrase.

Do you know if the Dog is potty trained? There is a good chance he might at first regardless if he is potty trained or not but if you set clear boundaries I don't see why it can't be managed. Dogs love to see what they can get away with.