As Scott says, the HOA fees are included in the 50%. Trouble is they can sometimes be VERY high. I looked at a listing for a condo here recently that seemed very cheap. Then I realized the HOA fees were quite a bit more than the P&I. You also don't really control HOA fees, and they can jump dramatically.
You certainly should buy your own landlord insurance, even for a condo. Yes, the HOA covers some things, but it won't cover something going wrong inside the unit. Further, you can have problems, like a toilet overflowing that can damage the building and other units, and without insurance you would be on the hook. Landlord insurance also gives you liability protection, and loss of rent protection.
You will have other expenses in addition. You'll have taxes, vacancy, and interior maintenance at the very least. You also have all the potential bad expenses like evictions or tenant damage.
The HOA fees SHOULD cover things like new roofs. If the HOA is underfunded, these things can turn into sudden, unexpected bills, though. Even it if is well funded, they can turn into higher dues in the future.
Personally I hate HOAs. (That didn't show, did it? :-)) They're OK if you a homeowner, and want to have that degree of control over your neighbors. As an investor, though, they really do nothing for you. You end up having to pay for all the same stuff you pay without an HOA. And, they may choose to do things you wouldn't do, left to your self. Essentially, you'll always have a partner in your investment. So, honestly, I would not, and do not, consider a condo.