Startup founders need their own version of a prenup. We had 3 teams imagine what they'd put in theirs.

If a founder's startup feels like their baby, their cofounder may very well feel like a spouse. Getty Images; Alyssa Powell/BI As startup activity rises in the US, founders face a crucial early decision: who to build with. BI asked three sets of cofounders how they built strong relationships and how they'd handle a split. They shared which conversations to have early, before avoiding them becomes costly. You've been imagining this moment for a while. Maybe spent weeks having long, potentially…