Two and half weeks ago we found a pup that had wandered in to our barn. It had been severely starved and looked like he had been abused. He maybe weighed 6 pounds and was shaking and every bone in his body stuck out. We truly did not think he would make it another day had we not found him. We brought him into the barn and gave him a fluffy comforter and water and food. Gave him some toys and let him rest in the barn. Now almost 3 weeks later, he has doubled his weight and is happy and playful, but still a little shy and afraid of people. He is very attatched to his "bed". He will not venture out of barn but only a few feet and look around before he runs right back onto his bed. We gave him a bath and he is thriving. My question is this: How do we go about potty training him. He will not go to the bathroom outside, he will go in the barn. I have just cleaned the messes up so far, but would like to teach him to go outside. We have just been very hesitant to scold him since we are positive that he was abused. I tried putting a leash on him to take him outside, but found very quickly he was not leash trained. I need to get a puppy collar because his neck is still very small since his weight was so low. Any help that anyone could give me would be greatly appreciated. Thank you.

A great deal depends on how much you want this guy to become your house dog. If he is going to be outside in the barn he will be very hard to "barn train" him. To start him off I'd recommend a slip collar much like a choker but made from a rope loop. Soft on the neck and adjustable. He needs time to build trust which means lots of human contact and exercise. How much time can you commit to this and will he become a house dog?

We would like for him to be an outside dog. We have had a boxer for 7 years and she is an indoor dog and a princess :) We have never been a two dog family because we treat our dog like our child and we do not have much room in our house. This pup will be treated with just as much love and care, just we don't have room in our small house for two dogs.
The barn floor is all concrete if that makes a difference so there is no dirt floor. I tried looping the leash to take him outside but he just pulled and jerked. I just don't want to scold him too much and I would like for him to be able to feel safe with us.

Never scold him for now, you are still building trust so don't blow it. That bed is his security blanket, he feels safe and secure there. Try walking him30-40 minutes after he eats until he does his business, then reward the behavior. When you put him on the leash have a treat in your non-leash hand and kind of show him or lead the way with the treat. When he walks with you keep the hand out in front and give him a tret every few feet. I am picturing a rural area, do you have access to any kind of dog training group in your area or a co-op extension service?

Yes we live in a very rural area. Yes we have a co-op but they do not offer that assistance.
I will sure give your advise a try. I am so appreciative of all the help I can get. I have only had two dogs in my life. Our first dog lived 13 years and our 7 year old boxer. So rescuing this pup is new to me. Thank you so very much for your help. I will let you know how I get along and keep you posted.
Thanks!