Most people would consider a lease agreement invalid if not signed by both parties, but the law doesn’t always see it that way. In Kansas there are actions that essentially create the expected effects of signing a lease - that an agreement between landlord and tenant for rental of the premises has been made.
Let’s say you give the tenant the lease agreement to review and sign. The tenant signs the lease agreement and delivers the signed agreement to you. If you never sign the agreement and provide a final, signed copy to the tenant but you accept rent from the tenant, the effect is the same as if you had signed and delivered the final, signed agreement to the tenant. Likewise, the same is true regarding the inactions of the tenant. If the landlord gives the tenant a signed agreement and the tenant doesn’t sign it and give it back to the landlord, but the tenant moves in and pays rent, the effect is the same as if the tenant did sign the agreement and deliver the agreement back to the landlord.
An important point is that if a rental agreement does take effect through one of the methods above, then the rental agreement is only effective for one year, despite the agreement stating otherwise.