I don't think there will be lending directly between entities with very different run speeds. If you're much slower, you can't keep track of who's worth lending to, and if you're much faster, you don't have the patience for slow deliberation. There might well be layers of lenders transferring money(?) between speed zones.

Almost on topic:Slow Tuesday Night by R.A. Lafferty. Recommended if you'd like a little light-hearted transhumanism with casual world-building.