Former owner of a failed business here! It was a chiropractic office, but it's still a sole proprietor business that closed in 5 years of opening...
Do you have AT LEAST 2 full years of absolute complete operating expenses AND salary for yourself? In cash, saved up, NOT a loan.
If no, don't open a store.
In my (former) profession, there were often non-compete clauses for newbies if they started off in someone else's office. So that's not unheard of in business. BUT. It would have been in writing, in a signed contract. Otherwise it's non-enforceable.
But. If she's going to go around snarking about you and telling nasty things about you and causing a stink, it's not going to be worth it to you...
Definitely check your town's laws on home offices. If you can open up for business, try to make a second entrance to your home, and have your stuff in that area. Don't give people full access. Many chiros like to have things out of their homes, but they find themselves hiding upstairs, b/c people have no boundaries. People will ring the doorbell at midnight b/c they fell down stairs...do you want people ringing your doorbell at 10pm because their little Suzie has a wedding to be in tomorrow morning and they forgot to get whatever it is you sell that would be good for that? No? Get a separate entrance. This will cost money, and will require permits...
My good friend went in, with a really good business plan, with husbands who worked and brought home all needed bacon, etc etc, in a fancy dress seamstress store...they made wedding gowns made to order, they did embroidery, they altered things, they were GREAT. They too failed after 5 years b/c of various reasons. (it's hard to go in with 3 people on something...) They had the money, the backing, the financial sense, the goodwill in their town...but still...most small businesses will close inside of 5 years. And it SUCKS.
Going into something like this where you already have, as someone called her, a bully...it's not going to go over well. Even if you toe the line, at some point she's likely going to think you're being sneaky in some way. It doesn't sound like the best way to start.
I'm so sorry I sound so negative. Sigh. I jsut want you to be prepared...not prepared to close, but to know that it could very well happen to you, and so you are totally prepared to open those doors and not make a CENT for 2 years...sometimes it can take a LONG time to start getting customers...
YOu're lucky b/c you have the ebay thing going...but if no one walked in those doors, could it sustain your place? Right now, outside my condo doors, there's 2 years worth of construction happening...to "beautify" it. We're not even halfway through, and the streets have been open the whole time to some extent. Already 3 businesses, long time businesses, have failed. Not enough traffic. This wasn't something htey wanted...business owners didn't get a vote in this...but it's happened to them.
So be prepared.
And even though I live in the downtown of my city, and even though I just talked about businesses failing, I'd go for the downtown (if financially prepared with saved up money NOT a loan) store and create a niche...