My borrower is refinancing the loan to hold the property (BRRRR) and I'm wondering if the new lender will have any concerns with this policy. 

Here in the USA you need what's called a "construction loan" and it's also very hard to find a company that will insure you if you're a newbie.

You would then have two loans, one on your home and one on the refi to access the equity on the investment home.Why not just use the refi cash out from your home loan for future deals? 

I have preaproval for a 250K loan now.

Last minute they changed the deal to a mortgagee loan and cut the SOW from $65,000 to $40,000.

Focus on understanding the rental market, conducting thorough property inspections, and leveraging owner-occupied financing options like FHA loans.

Refinanced August 2020 into a 15 year loan at 3.375%

Most agency loans will expressly forbid such an arrangement, so if they found out, the odds of having the loan called would be very high. 

I will be furnishing one side for now and leasing to a mid term rental until i get a property management company that will work the property or get it leased out to students What was the outcome?

The investor either gets a loan or buys the property in cash.