I have a neighbor who has a child the same age as my DS. We share a garage as we live in a duplex.
I have no problem with her LO playing with my son's toys that we keep in the garage, and vice versa.
However, I DO have a problem when they do not put them back or take proper care of them.
For instance, my neighbor filled my son's pool up and let her LO go swimming. Fine, I do not care. BUT, she did not empty the pool and she did not put it back. It is a plastic pool and hard to empty, but her BF could have easily lifted it and poured out the water. It sat out back for half the day and overnight without them using it again before I had my brother help me empty it since I cannot tip it myself.
Same with other toys..they get them out, but do not put them back.
Now, I recently got my son a picnic table. It was used and I got it for free so in all honesty I do not care if it gets ruined. But that does not mean I want my neighbor to use it and leave food on it without wiping the food off. Which she did, more than once.
Now, I have put my son's pool in the basement and his picnic table there too. I have told her before, I do not care if you use them, but please put them back or clean them up if you make a mess. She says OK but does not do it. If my son uses one of her LO's toys, I put it back.
My mom thinks I am being selfish not leaving the picnic table or pool out there. Everything else you can't really make a mess on or fill with water so I left those in the garage, just moved my picnic table and pool downstairs. I should not have to empty the pool or clean up a mess when my child did not use them.
She isn't a very clean person in general, her house is dirty and so is her car (like food everywhere-things not picked up, crayons all over the wall, dirty dishes, etc) She says her BF does not help and she can't do it all herself. But that should not stop her from emptying a pool or wiping off a picnic table.