At the moment my personal credit score average is about a 660, before the month is over I'm predicting that it will go up.

It sounds like you've got the "why" of your goals figured out, something that's incredibly important and often overlooked.

My situation is I have a decent down payment of 15,000 and a great credit score but can't get a loan without a co-signer since I don't have sufficient income.

I checked FICO scores, verified employment, you name it.

I haven’t had much luck but my local Bank Of America quoted me a 4.75% (4.85APR) 30 year fixed conventional mortgage 25% down on a $300,000 loan for a duplex investment non-owner occupied.I make around $70k/yr and have a 750-780 credit score and I do have a 2+ year credit history.

Again, my goal is to get as many rental properties ASAP.I have great credit score and good income.

Private & Hard Money Lenders provide 80% of the Purchase Price on rental properties with FICO over 700 - the LTV reduces the lower the FICO score is - for Fix & Flips they provide 90% PP 100% Rehab

I wondering what options are out there if I have six figures to invest, 750+ credit score, and real estate experience as an agent.

You (or your spouse, if you’re working together) may even choose to become a real estate agent in order to gain access to the incred- ible tools that agents have.

Someone with a 600 credit score could be great for a $800/month rental but I would consider it a big risk in one renting for $2,000.