Looking for advice regarding potential INHERITANCE SPLIT

[Kate Pasinelli]

Looking for advice regarding potential inheritance split. 

My father took out a $320K home equity line of credit (HELOC) to invest with my brother and I. We didn't find a joint investment, but I found an off-market deal and invested with my dad separately. I used half the HELOC ($160K) as a down payment on a 12-unit property, making my dad a 35% owner since we used his funds. My brother had access to the other $160K but ultimately purchased a 4-plex two months later using his own money instead.

Currently, its written that if my brother doesn't use the funds then he gets 160k value from the estate extra, as I used my half already but then my dad suggested a 2% annual appreciation on that amount seems fair on the 160k for him, and now he believes it should match his home’s appreciation, which is roughly 5% per year. My dads portion of our building will be gifted to me in the will FYI.

As a real estate agent, I see 5% as a reasonable market appreciation. However, I’m actively managing my investment, taking on risk, and improving the property, which has significantly increased its value. Does this arrangement seem fair? I’d appreciate any thoughts. Thanks!