I haven't heard of a problem with male friends coming to visit. I f asked, I would advise them to say they are staying with friends. The idea of a single woman living alone to most immigration officers is like the age-old "joke" about the father bringing his boy into the hospital and the doctor saying, "I can't operate on him, he's my son!"

I have heard the occasional problem for a woman visiting without a hotel reservation (this was a colleague about a year ago). When asked, she said she was visiting her brother and was asked to give his villa number and phone number and that was that. As long as she knew she had somewhere to stay, then she couldn't be a prostitute. (She was also a reasonably young and attractive woman).

But never volunteer more than you have to in any immigration scenario.