I am purely answering as a girl who lived with a Premium friend in one of those Premium Homes, I'm not an expert, nor 100% sure on anything, and I'm also not a premium player...BUT...
What I know is that most of those homes have a security system, most of the times located next to the main door. There you can choose who can tp whenever they want, if the house is off limits for everyone until you let someone in, etc etc...those homes are very safe and the sexurity thingy is very easy to use.
So no, probably you won't need to buy a security system on the market, the houses come with one. I think!!!!
Hope this helped!
xx Mags.