How easy to stop people from having "permanent guests" or subletting??

Other

Im suspicious of every applicant so far regarding my property thats recently been put on the portals. Its a huge house and I think many of the applicants plan to sneak their extended family in.

One of them have even said they have guests from other places all the time and their children come and visit with their own large families. How can I tell if it's just visiting though? If there is more than one spare bed? how do i prove this?

Also do they get fined for this? How do I stop them if my worst fears come true? Wait 6 months for an eviction? Insist on inspecting every month? Can I start charmore with a tenancy clause if I iscover they senak more people in?