(We're using it for a downpayment + rehab for an investment property).The tech issues with the bank have made this a terrible, horrible slog.   

The process is getting allthe information together like the 1003, credit authorization form, bank statements, income statements etc. they will underwrite the file and confirm the borrowers ability to repay.What state is this in?

A 60-year-old woman with great credit, rental history, and 20 years at the same job?

And pay another set of closing costs.If you do have to refinance in 5 years, the main concerns would be to make sure your credit is good for the refi. 

What is the credit requirements they look at?

Closed-end private equity style offerings generally have very different liquidity profile than a private credit fund (or interval funds), where the investor lock-up period is generally longer, with most of the returns being generated at exit (or back-ended).

I have great credit, killer salary, and a bunch saved up but still can't afford a 20% down payment on anything over 600k. 

Just wait until a sec 8 tenant fails to recertify or loses voucher and you need to evict these people who have barely any money/credit to find another place.

If you have decent credit (north of 680), you should be able to get 75% loan to value, assuming the DSCR is met (usually a 1 to 1 measurement between the PITI and the Gross Monthly Rental Amount).

They also have accountant access to my bank accounts and credit cards, so everything gets reconciled.