Help organizing heloc, mom loan, and brrrr strategy please

[Zac Boelkow]

Looking for advice, suggestions, and tips on how to pay for two properties I am currently in contract on. I am using my HELOC and Bank of Mom for both properties from one seller.

Pickering Ln: SFH purchase price $125,000

Watterson St: Duplex purchase price $100,000

Heloc contribution is $100,000 @ 3.5% interest only

Bank of Mom is $125,000 @ 3% 

One question I have is how to draw up "BOM" money. Should I write her up as a 30 yr schedule with a three year balloon mortgage or a 30 yr schedule interest only with a three year balloon?

Also on my HELOC does it make sense to just pay the interest only the first six months until I cash out refi?

I have never done BRRRR and so far have been able to buy property using my own cash and pay 100% every time. This is my first time scaling and I am confused on why and how to navigate this transaction as I never used debt prior. Also these property values should be close to $300,000 so I may be able to get cash over actual purchase price...

I am thinking that I would like to get the HELOC money back ASAP so I can re-use that capital for the next opportunity..