I'm always toying with the idea of starting an online "boutique" musical instrument store offering vintage/rare/classic/hard to find items. I'm semi-addicted to buy/selling/trading gear on craigslist. I'd be in heaven if I could profit doing so. Technically, I have profited doing so, but on a very small, personal scale.
I'd do repairs & restoration myself, and offer a service to find specific items people were looking for, as I also love the searching aspect of it. $10,000 should be plenty to get a cool website up and running and acquire some gear to offer for sale. I'd use ebay, craigslist, and be active on forums featuring Fender, Martin, Gibson, etc. Additional items would be added as acquired.
I know it's not a unique idea by any means, but it would just be a part time thing to do for personal enjoyment and hopefully some profit. Would never get rich, and best case scenario is maybe if I executed it well enough I could grow a decent reputation as a go-to resource for items like this and my "find it for you" service would be popular among those who just don't have the time to scour the internet looking for what they want. Worst case scenario is I end up with a bunch of really cool gear in my basement, which isn't so bad. I'd sell it all eventually, or just keep it. Seems like kind of a no-risk, all reward scenario for me based on my interests.
You should be able to start up a shopify store pretty easily selling this stuff. This is a perfect idea for a small e-commerce site. You probably don't have many products to add, and it should be easy to keep up with. You just have to take decent pictures of the product, and write some content with keywords. A niche product like this should do well with a good site.
I like this idea Satch. I see you bringing two primary values to a business like this.
1. It's a centralized "hub" where buyers and sellers connect. That's one of the incredible levers the internet makes possible - Easily connecting people that 20 years ago would have had a much harder time connecting. Whether it's dating sites like match.com or rental things like AirbnB, the principle is the same.
2. Curation. eBay already does this in a general sense bringing buyers and sellers together. Where your business could differ is if it became known as you being an expert on the topic. People trusting someone that's an expert like you when they're buying an old violin is going to be radically different than if I were selling an old violin I inherited and knew nothing about it.
The big hurdle for online sales is trust. Once you establish that trust, you'd have a huge advantage in selling items like this.
So if I were trying to start a business like that, I'd first set out to start establishing a reputation as a smart and trustworthy old musical instrument guy. I'm sure there are forums out there. You can have a blog writing content helping people looking to buy / sell an old musical instrument. Start an Instagram feed with cool pictures that would interest the kind of people you're looking to connect. Basically whatever it takes to establish you as a trustworthy expert. Once you have that, connecting the buyers and sellers should follow.
Good luck,
J