I haven't found a way to do it, so I'll just assume there isn't any function like this in the game (please fill me in if there is something like this).
I would love to being able to see the castle beforehand that I eventually might buy.. It would be a real downer if I payed like 20,000 for a castle, and then it's nothing like what I hoped for. One way of doing this would be to let the castle vendors decorate a demo-castle that you can visit and walk around in, to see how it looks
that would be cool i would love to see befor i buy it i was not happy after i bought the grand palce in mooshu my last castle was bigger then that place but ya a open house would be a good thing to add
I am currently working on creating videos of all the houses for this reason. I'll add my first one tonight to youtube. Try search for "wizard 101 homes"
Indeed, it would be nice to see what the houses looked like before you bought them. The best thing to do in the meantime is have someone, who already has the kind of house you're wanting, give you a tour of their house so you can see what it's like.
My personal opinion on the houses is this: stay away from DS houses, they don't give their money's worth :(; the inside of the DS mansion is just 1 big room (its only perk is the dungeon) while the other DS house is basically a tower with 3 stories of small rooms. MS houses are best for those who like the outdoors, with their bridges, waterfalls, and ponds. The Krokotopia houses also have lots of outdoor space but I don't like the atmosphere (thus I go with MS houses for this reason). I really like the cave inside the KT mansion though. The WC mansion has quite a bit of indoor space, and it has a theater to boot. The Marleybone houses have the most indoor space though. The regular house has, I think, 2 room areas and a basement. The mansion, on the other hand, has 3 stories, a basement, bridges, and a greenhouse (that you could make into a house of its own, like i did ). I just wish you could swim in the water at the MB mansion.
This my take on the houses. Your opinion will probably be different from mine though.