Chicago Region BMW Motorcycle Owners Assoccrbmw

I'm shopping for my first motorcycle. There's an ad for I bike I'm going to see later this week and I just realized it says, "2 into 1 exhaust" for a '75 R60/6. A little research and I can't find any indication that BMW made that configuration so it must be aftermarket.

Question is: How do I judge if this is a liability and plan on replacing it (and lowering my offer) or it's good? What are brands to look out for? I don't much care about originality, just reliability and completeness. Any tips?

Thanks,

-- Aubrey Granner