This is because it is so competitive and everyone wants to pull out of deals non stop.

Would it make sense to purchase (and try to get a deal) with cash then borrow for upgrades or should I finance everything and keep my cash?

Cap rates are really low and you don't want to be the last one holding the bag if the music (appreciation) stops.

PLEASE educate me, I do not want to make a rookie move, but I am having a hard time wrapping my head why borrowing money (and paying all that interest) is better investment than cash sale.

What happens when the person buying the property stops paying, or the local market crashes.

They would bring the down payment 0f 20-25% from their SDIRA and the LLC would borrow the other needed funds of 75%-80% using a commercial loan that does not need a personal guaranty from them at all (since that would be a prohibited transaction).

I told her no but as is the usual and customary practice the WD and DOT were.She said the first thing the the underwriter asked was if it was recorded and I said I'd never recorded the now and none of my other borrowers had any difficulty in refinancing.

If the borrower is under water on the loan, then there may be a chance you can get a SS done but will need to convince the owner to work with you on this.  

The seasoning period of the lender matters = 6-12 months is most commonif you use delayed financing (for SFR) you can do no seasoning period but can only borrow what you put inI've had some 7 month BRRRR, and I'm currently doing one I think I can wrap from close to refi in <12 weeks total.Knowing the type of property, rehab, and finance strategy will allow you to narrow down your expectations quite a bit.

You the borrower are personally 100% responsible for the payment, the rates are even based of your credit score.