My ex was friends with a researcher at a University abroad, who was invited to do a research stay where we lived. At the end he couldn't come, but he sent his BIL, who was working in the same subject. Exh said to him, "if he need some help, tell him to give us a ring".
So, one day the phone rang at 4 am, the BIL arrived and wanted to be picked up from the station miles away. He had not booked somewhere to stay, so exh let him stay while he got himself sorted.
He stayed with us for almost 4 weeks, wouldn't help with anything in the house, he often cooked paellas a but never big enough for us to share, even when he was using our food. Never cleaned the kitchen afterwards, made her bed or pick up wet towels from the bathroom floor.
If he sat to eat with us for dinner, he would do so in silence, although once he started weeping saying he missed his home (he was in his 30s). If we had visits, he would come into the living room, sit with us without acknowledging anyone and turned the TV on.
He said he couldn't pay for anything because he couldn't open a bank account (true if you are not here in a more long term basis) but he didn't seem to be in any hurry to get money sent to him.
I didn't put up with this kindly, but my ex didn't want to offend his contact abroad so he kept cleaning after him and driving him around while he was there. At the end I told my ex that if the guy was not out by the end of the week I would put his stuff out and tell him he had overstayed his welcome and leave him out.
So, ex took him to check flats, shared houses and eventually paid the deposit for him. Then he rang me to ask if I could buy him some bedlinen because he didn't know how to get it (I said no, but I could have bloody tell him that I couldn't get how he was working in a PhD if he couldn't even find bedlinen in M&S!). In all the months he was around he didn't produce a single piece of publishable research, but claimed that some important work of my ex was plagiarised from him (fortunately that work had been published a couple of years previously so he looked as an idiot.
We really felt a huge relief to know he was gone. We thought it was the end of it, but no... He contacted ex the year after, to say that he wanted to come for another research stay and sent me a message asking me to find them a place to live as he was coming with his wife, he also told me that the dog was a Great Dane that have been mistreated as a puppy and therefore was very sensitive and prone to attack people when it was nervous but he couldn't leave it at home as it was like a son for them.
My ex told him that given his lack of research output in the previous year, the university was not interested in offering him space. It totally went past him. The only thing that saved us from this misery was to point him out in the direction of the quarantine laws of the U.K., once he knew he needed to leave the dog in kennels for all his stay and pay for it, or pay £££ for a pet passport, he desisted of the idea.