Make sure that the break with your ex-co-founder is a clean one, i.e. ensure that company ownership, IP rights etc is resolved in a way that leaves no room for doubt at some later point.
You should try to avoid a situation where he can return at some later point with a potentially legitimate claim to a part of any business that your company may have evolved into.
You should try to avoid a situation where he can return at some later point with a potentially legitimate claim to a part of any business that your company may have evolved into.