Uuma, what a lovely idea! I can picture it already . . .
The answers to your questions are not simple ones, unfortunately. If you are seriously considering this, you are going to need to do a great deal of research first. Here are some things to consider.
Amount and value of inventory are numbers none of us can give you. A shop here in my small town in rural Texas is not going to cost anything like a small shop in San Francisco, Cali., or in picturesque Bar Harbor, Maine, or Bath, or Paris, or County Mayo. It will be very location-specific, and can vary widely in a given locale.
Considerations: A lease. Rent for the shop monthly. Utilities, phones, fax, internet. These constitute "overhead". Then there are fees -- sales taxes, use taxes, bubble tax, and any other tax your local government can dream up. You'll need a register, counter space, and furniture for displaying wares. Pricing "guns" labels, storage, gift wrap, and so on. You'll need a business bank account, and these days, it's hard to get by without accepting credit cards, as many people no longer carry cash.
Your local chamber of commerce or business council can give you some ideas of "cost per square foot" and "sales per square foot" to get started with. If your store costs roughly, say, $100 / sq. ft. to RUN monthly, you'll need to SELL $200 / sq. ft. monthly. That will give you just enough to keep supplied and a teeny-tiny margin of safety. You'll need to do more to actually make a profit to live off of.
Depending on your health codes, a sit-down-and-drink-tea shop may not be possible. This rolls into food service and is a whole different maze of regulations. I can almost guarantee you will likely not be allowed to *make* soaps and toiletries in the same kitchen you are using for food service. Prepackaged tins of tea for sale, along with cozies, teapots, cups and saucers, etc., are a different matter. You'll need public restrooms.
It sounds more like a "gift" shop to me, personally. Teas, tea "stuff", soaps, lotions, lip balms, cards, gifties, maybe some local hand crafted jewelry. I can see this being successful in a shopping area with neat old restored houses or shops, rather than a mega-mall.
A more and more common approach these days are "co-ops" (stands for "co-operatives") where a group of small shops get together to rent a space and handle some of this. You rent and decorate and supply a "booth", and the co-op handles sales, taxes, utilities, staffing, etc. as part of your monthly "rent". They monitor your sales and pay you for what you sold, less the fees. It can be a good way to try out your ideas. Consignment shops or wholesale may be another way to get your feet wet.
What you are talking about is absolutely do-able. But it's going to take an easy 6-12 months of preparation, not counting soap making time, to get ready to go. And count on being at the shop every minute it is open, plus an extra 2 hours a day, at least. You can't afford to hire help until you are making a real profit.
I'm not trying to scare you away, at all. I think your concept is a good one. But there's a lot of "hidden" work and expense in these things that many people are not prepared for. (Ha! Ask me how I know this . . .
) There are also many resources out there for you. There are lots of people who do nothing but help small (micro, nano, atomic) businesses get off the ground, ESPECIALLY if they are woman-run, local, handmade, etc. Get some great batches together, cut them in sample sizes, collect some data, and go start talking to people. At the very worst, you'll have learned what you DON'T want to do, gotten your name out there, and drummed up a few new customers. Small business people like to help one another. You can find all kinds of info on the net on business proposals, business plans, etc. Be prepared for detailed questions on your costs, $ amounts of sales, time in business, personal finances, etc.
Keep us updated on what you find out, and decide to do. I know there are several of us around here who have similar dreams. Good Luck!
~HoneyLady~