Unlike others, I say have a team in place from contractors, lenders, or bank for a refi, management company.

Does anyone know a bank that offers interest-only HELOC on a rental property?

Payment is in your bank by the 1st or they can’t stay.

I have heard of some podcasts saying “the bank wouldn’t give me a loan so my parents took out the loan.”

Should I have all expenses and income in one bank account?

However, I believe in most states if you can locate his bank account that there's an avenue. 

If everything else fails, you can mail them a burner phone with your number..As far as funding family money will probably be your first choice for both the purchase and the rehab.

As I think though the Math...If a property that is worth 5.3 million today at 6% cap approximately, at 5% interest rate; if the same property I could get at 4.3 millions in 2 years if the market falls, then interest rate possible at 6-7%, my cash on cash may be better but still not significantly better due to the higher interest rate, plus opportunity costs of sitting on capital for 2 years (1.3 million investment earning 1% bank interest instead of 7% COC if invested, loss of tax break depreciation, total loss may equal 200k loss in profit), plus increase in the rents and some value add could increase the cap from current 6 to 6.7 or so.

It's not out long enough for a bank or credit union to see return. 

They will take a percentage of anything they collect and there's no guarantee they will collect anything.An attorney may be able to assist you with collection action via wage garnishment or bank account garnishment.