However, the bank indicated they cannot finance the 6-unit property and I would need a commercial loan for it.

Using the fix and rent loans and 100 percent renovations how much does such a loan costs?

It's the same work to do a $50K loan as a $500K loan so the fees will be higher due to the loan amount but will still be much lower than what a lender or broker gets paid on a higher loan amount.

Another option is to take out a bridge loan for the rehab, then refi and take out a smaller amount of the $750,000.

It's ideal that you own the property outright because the holding costs on a hard money loan a lot of time is what kills development deals. 

Buying under an LLC shifts the type of loans you would be eligible for, and likely rules you out of considering a house hack or using an FHA/VA loan, but opens up different funding options if you have the capital for a larger down payment.

From my experience, due diligence is part of the difference between the two and the interest structure (Dutch Loans vs.

how to know if it is a good thing paying cash  instead of contracting a loan?

What type of loans or lenders should I target to get this deal locked in?

Seeing how little of principal is paid off in the beginning of the loan cycle, my urge so far has been to throw what I have as extra payments chipping away at that mountain, but I’ve been also thinking lately if that’s a wise practice.