Short answer. No. Under the Civil Code, acts relating to possession executed by a person who holds property merely as a caretaker do not bind or prejudice the owner unless the owner gave express authority for those specific acts, or later ratified them. Without authority or ratification, the deal does not bind you.
What the law says
Acts relating to possession, executed or agreed to by one who possesses a thing belonging to another as a mere holder to enjoy or keep it, in any character, do not bind or prejudice the owner, unless he gave said holder express authority to do such acts, or ratifies them subsequently.
Civil Code, Article 558 — Acts Of A Mere Holder. Read the full provision →
The distinction between a possessor and a mere holder
The law recognizes different relationships between a person and property. An owner possesses in his own right. A lessee possesses on the basis of a contract that gives him a real interest. A caretaker, however, is a mere holder — he holds the property for the owner's benefit, not his own, and has no independent right over it beyond what the owner delegated. Article 558 is written precisely to protect owners from having unauthorized acts of their caretakers or custodians used against them. The phrase "in any character" confirms that the rule applies regardless of what title or label the holder carries.
Express authority is what matters — implied is not enough
The two exceptions to the rule are: the owner gave express authority to do the act, or the owner subsequently ratified it. Implied authority is not mentioned — and that is intentional. A caretaker hired to watch over a house does not automatically have implied authority to rent it out, sell access rights, or agree to easements, just because those acts relate to the property. If the owner did not specifically authorize those acts, the caretaker was acting beyond his remit. Third parties who deal with a caretaker without verifying his authority do so at their own risk.
What subsequent ratification means
Even though the caretaker had no authority, the owner can choose to ratify the act afterward. Ratification means the owner affirms or adopts the unauthorized act as his own — essentially treating it as if he had authorized it from the start. Ratification can be express (the owner signs or confirms) or can be implied by conduct (the owner accepts benefits from the deal or acts consistently with it). An owner who knows about the unauthorized act and says nothing for an extended time may risk being found to have ratified it through inaction, depending on the circumstances. If you do not want to be bound by a caretaker's act, act promptly to repudiate it.
Protecting yourself as an owner
If you have a caretaker, put his authority in writing and be specific about what he can and cannot do. A written instruction that limits the caretaker to maintenance and security, and explicitly prohibits entering into any contracts on your behalf, is far more useful than a general employment arrangement. If you discover your caretaker has entered into an unauthorized agreement involving your property, document your repudiation of the act in writing and communicate it to the other party as soon as possible. Delay in disavowing an unauthorized act can complicate your position.