Welcome to you and Hero! He's VERY cute! You're going to love this website because there are so many knowledgable members who are very friendly and willing to share advice. Our Daisy Mae will be 16 weeks tomorrow - about the same age as Hero will be when you bring him home.
I agree with Cicero's Mom - - get Hero a crate to be his "den". Ours fastens on to the ex-pen - so it actually increases the space.
We work out of the house - so Daisy usually
goes potty outside since we're home and take her out numerous times during the day. However, there are times we need to be gone and Daisy will potty on a K-9 grass tray. We restrict her to the sun room (fence it off with an ex-pen) and we put her crate out in the sunroom. We actually carry the crate around the house with us! We bring it in the office when we're working - and then carry it in the bedroom at night. We set an ex-pen up with the crate in our bedroom and put the K-9 grass tray in the ex-pen for her. She gets up and "goes" in the middle of the night, but climbs back in her ex-pen (den) and sleeps in until 8:00 AM!
Daisy climbs in her crate for naps when ever she's sleepy - unless she falls asleep on top of my foot while I'm on the computer! LOL! Her crate is her "safe place" and she curls up in there if there's a storm etc.
She's not 100% on her potty training. Mistakes happen usually because I am busy and put off taking her out and the potty grass isn't in the same room as Daisy. Puppies just don't have a lot of time to get outside once they realize they need to go! If Daisy is in the same room as the potty grass, she doesn't have accidents. It's when I've let her run loose (and haven't watched her closely for signs she needs to go) that she's had accidents - totally my fault!
We hope so see more pictures when Hero comes home! I bet you give him a "Hero's Welcome"
(forgive the cliche!)