I have about 10k in federal loans and 6k in private loans.

I'd like to consolidate - do I need a cosigner to consolidate? I don't have anybody who can cosign for me -which is a problem.

My credit score is in the 600s, never late, paid double minimum due if not more, etc. The high balances on all the loans (I think I have 6 total) is killing my credit score and I'd like to start a business soon.

You generally can't consolidate private and federal loans together. Even if you could, it probably wouldn't be a good idea since a lender willing to do that would most likely give you less favorable terms than you have on the federal loans now. If you really want to consolidate, I'd recommend getting one consolidation loan for the federal (preferably through Direct Loans) and a second for the private if you can get approved.