If the property appraises for $500,000, you would only be able to cash out $375,000.Would this still be true as a primary residence or would we be able to find something like 5-10% down on a 30 yr loan?

IF it's too good to be true, then it IS!

I get calls, texts, cards and letters constantly on this rental.

As such, many aren't incentivized to advise you along that path (sad but true).

True if it is not negative cash flow.  

True off market deals are ones that you find yourself, direct from the seller without a wholesaler or any other middle person involved. 

Maybe with automatic payment stuff and you can request changes to your credit card due dates, you can take as much advantage of the float. 

I see 3 days ago a charge for a whopping $390 was charged from BiggerPockets to my card.

True, another good option is to link forces with another wholesaler and advance it together.Good luck!

Bottom line, if it sounds too good to be true, it probably is.