HELOC BRRRR and CASH OUT REFI

I am a newbie real estate investor and will be using a HELOC to pay for the purchase of a house including rehab costs. Couple questions below:

1. Should I be getting preapproved to get a cash out refi, will the banks even consider this if I haven't even purchased the house yet? 

2. How do I figure out the BRRRR calculator for a HELOC? I have been selecting the cash button for purchase, but then that isn't counting the 4.5% interest I will have for the HELOC.

3. Are banks even allowing refi's right now due to the Coronavirus?

Thanks in advance for your advice.