For a more accurate financial projection, factor in these additional expenses separately.

If you refinance the property now the loan would be $100K at 20% down and $80K would have gone to repay the original loan.First, if these are your numbers for rehab cost and after repair value, it is probably not a good deal to begin with and you shouldn't be doing it.

I have an SBA loan on that one and it only cash-flows me a few hundred dollars a month.  

Considering the investment size and projected returns, how should I structure my financial involvement to balance the potential risks and rewards?

I am focusing on trying to find off market deals and working with creative finance since expansion is slow moving based on my salary, and I'm too impatient to wait for the duplexes to earn another down payment.Is there a financing option that I am missing to get a loan for a down payment?

I am wondering is there any hard money lenders that can provide 100% financing on investment property and also provide rehab loan for short time period?.

The loan can be structured with no pre-payment penalties so your not tied in for a handful of years.  

My dilemma is that I worry that commercial lenders won’t fund any renovations or wrap it into the loan.

I would assume the mortgage would need to be changed because it's a personal loan. 

Beware that if the loan amount you need is very low  ( sub  70K ) -  there are many lenders that cant/ wont be able to do the loan .