Do I need my own home insurance if the HOA has a master policy?

Yes, you usually do, and it is easy to overlook. The building's master policy covers the structure and the common areas. It does not cover your finishes, your personal belongings, or your liability inside your unit, and that is what an HO-6 policy is for. Newer rules also push more of the building's deductible onto the building owner, which lands on everyone through the dues. Carrying your own policy is part of the true cost of a condo, not an optional extra.