My landlord is willing to redo my kitchen but says he will raise my rent a percentage of what he pays for the work. Is this legal?

Only once your lease is up and it is time to renew the lease. If you need the kitchen redone ASAP and he can not/will not do it without raising the rent before then you may have to negotiate a compromise. But he can't just, surprise, up the rent on you. And I don't think he should raise it until the work is totally complete either.

If you have a fixed term lease... then no its not legal. If you rent without a lease or month to month then he can raise it with 30 days notice.

He is willing to do the upgrade, did you ask him to do an upgrade? Sounds like maybe so. Terms of a lease can not be changes unless both parties agree to the change. Maybe he is saying I'll give you a new kitchen but you will need to help with the cost by paying higher rent. If you both agree, it is legal but the written terms must reflect this change and be signed by both parties.