Yes you can have a lodger. Your tenancy will allow you to sub-let part of your home i.e. a room with our consent but you cannot sublet the whole of your home.
If you are in receipt of housing benefit or Universal Credit you must update your claim. Depending on your lodgers circumstances will depend on how much your benefit claim will change.
If you do not declare your lodger’s income details you will be committing benefit fraud so it is very important you declare this change immediately.