@Shmuel Waldman In my experience partnership splits are determined by the size of the deal, a 6 unit deal is going to have a different profit split structure than a 60 unit deal which will be different from a 600 unit deal, What size deal is this going to be?
If it's a small deal, A fair way to structure the profit splits will depend on a few other things, If all four (4) partners are bringing in the same amount of equity (6.25%), at that point the profit split is simple (25% each), It's what's happening with the other responsibilities of the deal that would determine additional profit splits for any given partner.
1) You mentioned that you're getting the loan yourself, Are you being compensated for assuming this additional risk on the deal?
2) Who found the deal? Is that partner being compensated for doing the research and analysis for discovering this deal and bringing it to the partnership?
3) Who's managing the deal and the partnership? Is that partner being compensated for managing the deal?
4) What's the exit strategy for this deal? Holding for a short-term 5 years or less then sell and split profit, refi and cash out partners at some point and the LLC maintains the property, etc... these different scenarios will yield very different profit splits.
A good partnership agreement will outline these responsibilities in addition to many more, these responsibilities can have value assigned to them, if this is your first partnership deal, keep it simple so these partners will brag about the great deal to other investors increasing your pool of investors.