Unfortunately, the law isn't going to help you. If you improve your landlord's property without an agreement beforehand that the landlord will either reimburse you or pay you for your efforts and materials, the fruits of your labor are the landlord's alone.

That's the result of an age-old doctrine of property law: Whatever you attach to the landlord's property, as an alteration or an improvement, becomes the landlord's property unless you have an agreement to the contrary. So unless your landlord is willing to be generous, you're out of luck -- and certainly out of any improvement money.