5% down sba purchase

I understand the other 5% has to be a full standby seller note. Heard a lot about this. But want to hear from real experiences how frequent this happens. I know the full standby tends to deter sellers away from participating. But I’m more so curious how buyers negotiate for this and if lenders require a certain seller note percentage to even consider this. From my understanding, it isn’t always 90-5-5, more like a 75-20-5 or something else.