Google, lots of googling. Typically I spend about a week looking through house plans before finally settling on one. For family homes, I like to use actual house listing like on Zillow, or realitor.com sometime they give you the floor plan with those, plus actual pictures of it being lived in. I like to use the thepinnaclelist.com for any kind of mansions or modern houses.
This site might help you, it lists lots of Victorian era floor plans https://www.architecturaldesigns.com/house-plans/styles/victorian