Good question. Which idea makes more sense? You could organize a survey to be distributed to a small group of people that represent your potential clients. See where the demand is and make your decision on that. The less-niche approach sounds sort of like Craigslist, which might be hard to compete with. For that reason, I'd probably go with the first idea. But you may want to survey your audience first.

Hello

This is a good idea. I think it’s great to have variety based on what you’re trying to do. Definitely would sound like a site people can sign up on and list their unsold items and with the right SEO you can attract these people and sell them memberships.

First, let me say I think you have a good idea. I think starting out, you should focus on niche. Considering your idea, the riche market you're going after seems to be quite broad (think of all the bakeries/cafes etc. you can find in just one major city).

By going niche, you can quickly become the "go-to" expert in the field. This will help with word of mouth advertising, referrals and especially Google.

Once you've mastered that model, you can consider branching out (including more categories) or duplicating the model for another niche.

If you go broad, you'll be competing with Craigslist, Amazon, Facebook, and a variety of other "generic competitors.

Great idea - good luck with it!

A business ideal with a good cause!

Either niche or a general marketplace depends on many factors:
1. how much money you have or can raise.
2. the management team's capabilities & networks
3. the outcome of the product-market fitness test
4. the level of operating challenges in handling the old items
5. Make a choice between going straight to build a business or split some resources to keep the company survive while slow down the building of the business.
6. The business environment that worth to consider

The points above not exhaustive, but relatively important to help you to answer your question.

Some will say that the right move is to specialize: to finely hone your brand to target a particular niche. The more in-depth your targeting, so the argument goes, the better your chance of convincing your target audience to buy from you. You certainly can’t please everyone, and it’s difficult to establish a unique identity while trying to serve multiple distinct groups.

Of course, others will contend the opposite: that you’ll get ahead by giving your brand common appeal and exposing it to as many people as possible. Niche targeting puts the fate of your business in the hands of a relatively-small group of customers.