Welcome aboard.
Cool bike,but what is the yellow thing under the seat on the upper stays?
Good luck starting a shop.
I haven't owned a business for years,when I did it was a recording studio so I don't think I'll be much help.
But I imagine if you're wanting to open a vintage bike shop,you'll have to spend money first. You'll need items to sell,so swap meets are in your future - a lot of them.
Then of course you'll need a place to put bikes and parts,so a storage facility,garage,barn,store front. Something like that.
With vintage bikes there's a huge variety out there and everyone likes something else.
Some people only want schwinn stuff,others want jc Higgins,so on and so forth. I myself like anything cleveland welding and murray tank bikes. So all you can do really is stock up on anything bicycle related you can find,I'd say 1990 and earlier. Just get as much as you can,you can start small by selling at swap meets and flea markets. Or if you have the finances for a storefront you can go all in.
Just remember,the first year for any business is the hardest.
If you want to open a new bicycle shop,well that's a whole other can of worms.
I hope this helps,even a little.
There are others on here who own shops,I'm sure they'd have some better input.
Again good luck to you and welcome to the site.