Lucara, Joe looks like a very nice mule. He's got nice conformation and he sounds friendly from your description. But I would not suggest you get him. You still consider yourself a beginner rider, right? If that's the case then Joe is not the right horse for you. Don't let his sweet personality cause you to make a decision you may regret later. It sounds like he has some serious training issues. That is not the kind of animal you need to get for your second horse. For that price you can get a much better trained horse.
Please take my word for it. My first horse was overpriced and undertrained, but he was beautiful and I fell in love with him. Though I have fond memories of him, he WAS NOT a good choice for my first horse. I learned a lot from him, but if I could go back and do things differently I would (Don't get me wrong, I really did love him). Stick with it, you'll find that perfect horse sooner than you think. Don't settle for something that's not perfect for you. Joe will find a good home somewhere else, he is a fine looking mule.