The kind of thing that doesn't make or break your project financials - ie perhaps the jurisdiction doesn't have a great chance of 'making' you do it, so you can take it on more from a 'bring upside value' to your rents, etc.... and you get some 'soft' experience working through jacking something, pouring 1x new footer for a corner post, etc.  

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?

In my jurisdiction he would be out in less than 30 days.

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

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.