Is a verbal agreement as good as a written agreement from the landlord?

Yes, unless you have to prove it exists.

Oral agreements can be just as binding and enforceable as written agreements, but it depends upon whether or not you have a valid offer, acceptance of that offer, consideration, and performance, or breach. The usual problems that can arise with verbal agreements are whether or not there is actually an agreement, what are the exact terms, and where there is supporting consideration. Sometimes any potential issues can be overcome by part performance as well. Whether or not you will have any issues depends upon the circumstances and alleged terms of the agreement. There could be issues of mistake, or frustration of purpose, or there might not be a contract at all but you might have a situation calling for "quantum meruit" or "as much as deserved" under a possible quasi-contract theory. You should consult with an attorney with the specifics to review what your rights and duties might be under an oral contract situation.