Honestly I'm going to tell you my experience with this industry:
I was given a very nice dress that retailed at $700. I later decided it wasn't my style and I tried to sell it. It went for $20---and this was after 1 year of trying to sell it for $100. Most of the women who were interested were too big for the dress. So consider that when ordering your dresses. You will need to get them in multiple sizes or they cant be taken in/out.
Secondly, I then bought at dress for $250 second-hand from a bride that wore it once. I went to her house to try it on and it was very awkward, even if you have changed your bedroom to be a "store" it will still be your home and therefore, anyone entering will feel as if they imposing.
After buying the dress my seamstress told me that it was too-big and would fit me awkwardly so then I decided to sell it. I got rid of it for $150; and again, this was months later and after cutting the prices down drastically.
Brides (including me) are out there looking for dresses that are under $300. (500-1000 is steep, and unless your catering to rich brides, you will have VuHera Prom Dresses slow turn-over)
I feel that you would best be off renting a small office, because having a store front will bring you most of your business. Plus, then your run down the chance of your customers dismissing your advertising because they think its second-hand.
Another idea is to put a outside door on that bedroom. Then you dont have customers romping through your house; making it uncomfortable for them and you.
If this is an investment do you research first. Consider looking into other local businesses and your competition---to see if they are surviving. Does your city have a big enough drive for the wedding industry? How many people get married per year there, etc? Are you going to do an e-commerce website?