When starting a Marketplace bringing together buyers and sellers of products/ services, 1)Is it better to start a marketplace that sells niche products (eg. selling blue widgets ) or all kinds of products? Or start offering niche products first and build up traffic/ users first and when more established then expand to other kinds of products? 2) Use off the shelf script/ program and modify or get a coder to write a script from scratch?
1) can work both depending on which niche you decide to start with, if the niche is big enough and there is enough stuff to be sold then just start with the niche and then expand. But the first way could also work. The most important thing for you will be to get traffic/users 2) depends on how much money you are willing to invest in the startup. small budget= shelf script and customise it bigger budget = custom script from scratch
I would suggest you should sell all the thing under one roof.That way,you can earn more money and your client can buy the thing they want under one site.Its keep their time saved. Try not to use premade script or template coz it will make your site look like other site and nothing special about it.Hire a coder and ask them to quote the price for you.
Its better not to do that but rather customize the already tested thing that has worked. You don't want to re-invent the wheel each time and you should always use the code and then go with someone to make it like you want it.