David Siedband ⋅ Palo Alto, CA Zentraal, Inc. ⋅ 12 years experience

You're unlikely to find something off-the-shelf. However, as this project is a relatively compact scope, you can create something custom with a modest investment of time or money.

I'd recommend building your first version in either Django or Rails. These are well-proven and stable technologies with a large pool of developers and good documentation. Be sure to leverage existing 3rd party modules+services for things like Social Login (e.g. Facebook, Google) and Payment Integration (e.g. Stripe). In that sense, perhaps 60-70% of your app comes from off-the-shelf modules, and you're really only building 30-40% that covers your specific use-case. So, you don't need to reinvent functionality which already exists.

Another way to reduce costs is to have things like your data-model, wireframes, and requirements docs done before you bring in a developer. These will also help you get much more accurate estimates, as it's much clearer to the developers what you're asking for. Free or low cost tools to consider are ERwin and Omni-graffle (modeling) and Basalmiq (mockups).

John Green ⋅ Cary, NC Information Technology ⋅ 40 years experience

That's the trick, isn't it? There are several stock trader applications that are a dozen years old on github et al that could be adapted to a crowd funding application model, but the source code is pre-html5, which is the standard these days.

There is really no way around the fact that modern applications need software development. Developing software is not without risk or reward, and takes capital.

Speaking of capital, do you have a business plan ?