the property’s rehabilitation is scheduled for completion in 2025 and the rent will subsequently increase, can I proceed with a cash-out refinance based on the current rent roll?

I won't proceed on a property if I don't believe I can hit a 10% gross yield.

In fact, approximately 40% of our business involves the Section 8 program.40%...

The IRS doesn't trust you to report accurate information, so the 1099 from the property manager is checked against your filing.Any company that does more than $600 in business with you should issue a 1099.

Working this backwards, what I see is a 3rd party trying to benefit from another’s house via rental cashflow, My only business is 30+ years as probate estate and trust lending in CA.

If you drop business and work you can bounce back.  

This will allow you to put the loan into the entity or business name of your choosing.

Operating within California means you’ll need to register any LLC conducting business in the state, regardless of where it’s formed.

However, this is not a cash out refi.Cash out refi is when you refinance an existing loan, with another one (i.e replace the loan) where there is enough money left over at the end of the process where you can put some proceeds in your pocket.When it comes to your strategy - just make sure you're being conservative with your numbers on the purchase / rehab if you don't plan on using other proceeds to payoff the HELOC. 

I've never seen such a mismanaged business.