@Samuel Pavlovcik has added a great deal of value in the past to folks looking to add units.

What creative financing strategies have you already explored, and how successful were they in helping you close deals?

You will have to put them all into a single LLC a week or two before closing, ideally they are geographically close together. 

Typically you can get a deal under contract and then go looking for financing.

He did a soft check and said my debt to income would not qualify me for a HELOC... but a cash-out refi with an FHA at 6.5% would be okay with around $100,000 cash-out which would put my debt to income around 56% <yikes, I know>  Since I literally just bought my house hitting the 30yr reset isn't a big deal... especially if rate is micro point lower.  

OR should I base it on a percentage of equity earned that is predetermined before we close on the property?  

After you cashed the check it got closed.

What made you interested in investing in this type of deal?

Most claiming to cover closings costs/sellers cost.

I've closed loans with entities way less than 6 months old.You have a long road ahead of you of you can't bring the capital or credit.