Can I get out of my personal guarantee by paying the landlord a lump sum instead?

Possibly, but only if the landlord agrees — a guarantee doesn't come with a built-in buyout mechanism under general commercial lease practice, so any lump-sum release is a negotiated outcome, not a right you can insist on. Landlords sometimes will accept a cash payment, an enhanced security deposit from the buyer, or some other form of additional security in exchange for formally releasing a departing guarantor, especially where the buyer's own covenant is otherwise solid and the landlord has little practical reason to keep two guarantors on the hook.

Whether a landlord is willing to negotiate this way depends heavily on their own risk assessment and how much leverage you have in the broader assignment discussion — it's rarely offered proactively and usually needs to be raised directly as part of the consent negotiation.

If a clean exit from your guarantee is a priority, it's worth proposing this kind of arrangement early, before the landlord's consent is finalized, rather than trying to renegotiate afterward. A Treadstone business lawyer can help structure and document a release on terms the landlord will actually accept.