ust got a new tenant from section 8, after months of searching, finally , we settled on these three sisters. We thought since they are young, maybe they would not have much experiences.  They only qualified for two bedrooms voucher, but i have a three bedrooms  singles house.  So on the rental agreement, I had wrote its a two bedroo0m house ,then on a separate agreement, I wrote one bedroom for the remaining portion  of the rent.  They agreed and signed both rental agreements.  But the garage is not included since I need it for storage of my tools and supplies.  They agreed.

Before they started moving in, the oldest sister asked if they can store something in the garage ( something they don't use)  I thought since it's so little, I let them .  

Yesterday, we went to the garage to store more supplies, we found out they8 were using my patio chairs for their thanksgiving party without even asking me if they can borrow them.  Then i looked at inside the garage, it was half full of their belongs inside.  Now, I realized I made a mistake by letting them using the garage, since now they are starting taking over.  I planned to have my power equipments, tools, and other supplies stored in the same garage but afraid they might use them without asking.  What if they get injured, I would be liable for it.  Besides, anybody can just come and take whatever they want, I would not have any proof.

I would like to get my keys back by giving them a legitimate reason without getting our relationship gone bad.  How should I go about it?

Or, did I made a mistake by giving them access in the first place?