HELOC with non- occupant co-borrower on first loan?

[Baird King]

We would like to get a HELOC on our current house to move on to buying the next one but we seem to be in a bit of a unique situation:

My wife and I bought the house with a partner because at 860,000$ (with 20% down) it was just a little above what we would qualify for on our own. We remodeled and then decided to buy our partner out so we did a cash out refi to pay him off. The house appraised for 1.2m and the new loan amount is 836,000. This time again were very close to qualifying by ourselves but in the end, in order to do the cash-out refi, we had my dad co-sign the loan (however his name is not on the title). 

We would love to access some of that equity to move on to the next property but after talking to a couple of lenders I'm a bit confused. Some said they wouldn't do a HELOC if there was a non-occupant co borrower on the first loan. That didn't make sense to me because those are two different loans. Is the problem the fact that we might not qualify for the new loan amount and can't have a co signer on a HELOC? Is the problem our debt to income ratio and not actually the fact that we have a co- signer on the first loan? So if in the meantime our income would have doubled we would be ok? Is there any way for us to get a HELOC?

Hoping to shed some light on the situation...thanks in advance!