Pretty bad credit will most likely keep you from getting a cashout investor loan. Both "casout" and "investor" are scary terms for lenders, so adding bad credit will most likely scare them off completely. That said, I have had people tell me they have bad credit and it is not so bad, but know that anything below 720 will make this a difficult loan to process.
So now what? Well, there are a couple of different choices out there for you. You mentioned that this is an investment property - so you also have a property that you occupy? Taking out cash on a property you own is easier than doing it on an investment property, so that is one option. Same with getting a line of credit. Lending on a personal residence is much easier and comes with a lower level of criteria.
You have Hard Money loans. If your current loan is low enough on the investment property (below 70% loan to value) a Hard Money may work.
Then, you can always work on your credit. Some things work faster and are easier to do than others when it comes to credit repair, so seek someone you trust and have them help you with that. Typical things that cause scores to drop (other than late payments or collections) are high balances on credit cards (anything over 50% will cause a drop in your score) and multiple inquiries on your credit . Those are quick fixes and can improve a score within a few months if done right. In fact, if you have them done today, by next month you can ask your lender to do a rapid rescore on your credit to see if the scores did rise to a point where the loan can be made. Good luck and Merry Christmas to you and yours.