What does altes Haus mean?
Was geht, altes Haus?
Does it mean “What’s up, pal”?
4 – Person, Mensch
er ist ein fideles, gemütliches, gelehrtes Haus
wie gehts, altes Haus (alter Freund)
Yes, altes Haus is probably best described as pal or bro. Someone which needs to a good friend or a guy from your clique you see regularly. I would say a good English translation, which gives you the right feeling is
You (maybe) souldn't use it at work, but with your homies it is OK.
The Great Gatsby says old chap in English, and altes Haus in at least one German translation that I have read (Johanna Elsworth — 2011).