Advice on a Rescue

If I were in your situation id keep the dogs seperated as much as possible, take them out seperately to potty and play. As for your new boarder id give him plenty of space. Just give him a chance to get the lay of the land. Let him make up his mind about you before starting any kind of training.

Right now he doesnt know you and probably doesnt trust you that much. Give it a little time and let him warm up to you and then start with some very simple training for short periods of time with some really good treats.

Work on something like sit, down, stay. A lot of petting and positive reinforcement to let him know he has nothing to fear from you. Remember , he came from a shelter, he was hurt and no doubt scared to death and now hes in a whole new place hes not sure about. Let him hang out for a week or so and dont press the issue. If he doesnt want come to you leave it at that, let him makes the first moves.

I guess thats enough to get you started. Im sure others will have their own ideas but thats what I would do.

Getting a rescue is more like getting a used car that needs some work.

You don't always get the full story on it, it has no guarantee, sometimes there's things that need to be invested in under the hood, and you can't just drive off into the sunset without a thought.

If not from a reputable rescue who has invested time and money into the dog, you will be the one who does that.

Feed him in his crate, give him great things in his crate-he needs to be used to that thing for HW tx.

Did the vet explain why no activity with a HW + dog undergoing treatment? Make sure you read up on treatment/aftercare.
http://www.houstonsheltiesanctuary.com/heartworm_treatment_aftercare.htm

http://www.grrh.org/13Health/health.htm#Heartworm%20Treatment%20Aftercare

Like Mom said-nothing to get his heart rate up. Keep things low stress/low activity/low excitement.

General info on first two weeks (after being in rescue-so make it 5-6 weeks for a shelter dog): http://www.brightstargsd.org/mainpages/adviseforowners.html

Congratulations! Take things slow and definitely keep the dogs apart until you know that your girl will leave it immediately and that this dog won't feel overwhelmed-and that you are their person and that you can trust what his reaction is going to be to things. DO NILIF! These dogs just don't throw their affection at anyone-you earn it through NILIF and they earn their priveliges and learn how to act that way simply and with clarity.

Not to mention you want to keep them pottying in different areas if you can-he may have worms (likely).

I would also ask how heavy his HW load is before neutering him, though I think it's great to do it ASAP-just make sure it's safe.

GOOD LUCK! Post pics!

Wishing you good luck with him! It was great that you saved him!

NICE on the crate!!!!

I hope you can get a discount on that hw treatment. It is expensive.