It's fine no worries. Not an inconvience in the slightest. No need to apologize. <3
As for your situation...The practical thing to do would simply be to kick them out. I know this is hard. We all want to be the nice person who lets them stay until they get back on their feet. But there is a point where enough is enough. You are not their mother or father and even if you were they are an adult. If they are making you uncomfortable in any way, shape, or form you need to tell them. If they are being ungrateful they can change their tune or leave.
As for magickal advice yes I would say shielding is most certainly a good idea. Donald Michael Kraig is a good book which has an explanation in it as well as many other things that might interest you as well. I will link the pdf down below for you. If it does not work it means there is a space somewhere in the link. Sometimes the site automatically does that when you post links so just take out the space if it doesn't work and it will. :)
For blessing you or your house and in many protection working I would suggest white candles, witches black salt, war water, smudging/sage, moon water, holy water. There are so many ways to tackle a problem! ^^
Donald Michael Kraig Modern Magick pdf: