Angel Investors - the refinancing process

[Phoebe Bright]

Hi there, 

I am looking to buy my first doer-uper property to rent out and am looking at working with an angel investor to help fund this. 

I am getting a bit confused as to how to pay the angel investor back in one lump sum (rather than asa monthly fee). 

I was told i could buy the property, do it up refinance and then pay back the investor and the fee's /money i had put into the house in one go. Then i would just have to get tenants in to cover the mortgage repayments and hopefully some extra = positive cash flow. 

I was wondering if someone could please help explain how the refinancing / remortgaging part works and how soon after buying the property you could do this?

Thanks!