What software should I integrate to handle the credit card payment on my app?

Yes Wix supports a mulitude of APIs to used for various fetch calls for your web pages. If you already have to API's in mind you can venture off within you WIX code to integrate within your application's processes. There shouldn't be any complications getting this done. Please see the link below for more information https://www.wix.com/code/home/api

https://www.filepicker.io/ is the best thing that you can integrate with this app which suits your requirement. If you are the owner of the app, you can integrate it very quickly. If not, you can suggest the app owner to do it Feel free to call me if you need more clarification. I am consulting architect for few companies in US and India on mobile, web and windows/linux/mac apps.

Well this totally depends what your MVP is? What's the functionality? I'd suggest something like http://www.squarespace.com/ our designers with very little technical knowledge have had great success with this. Another option if it's just for demos/feedback is to use something like http://www.invisionapp.com/ for rapid prototyping.

I hope this answer will help you in two ways: It should help avoid unnecessary expense being incurred and it should also help you recruit software engineers to build your project. Before you spend a single dime on building, I'd encourage you to validate the idea itself with potential customers. Identify the kind of person you are thinking of solving a problem for, and just explain the high-level concept. Make sure that a sufficient percentage of them are saying "yes, I need this." Then, really distill the idea further into a single piece of functionality that this customer base says they want. There are tools that allow for "drag & drop prototyping" like fluid.io that you can use to create a clickable walkthrough of the user flow you're looking to create. The more that you can do to validate the idea and focus it, the more you can define your "Minimum Viable Product." If you can't find enough of your potential customers to get excited about the idea, I would advise against hiring anyone to implement anything. That said, it's also a lot easier to recruit talent when you can say "I spoke to 100 potential customers and 40 of them said they would use this" or better yet, pay for it. Convincing anyone to work on your idea will be considerably easier if you can show some existing proof or interest around the idea. From there, your best source (assuming you don't have a network of people to draw from) might be local colleges & universities. I would advise against hiring online or working virtually with someone when you are new to building product. I'd be happy to talk to you about your project, how to validate the concept and how - if you decide to pursue it - to hire good talent. Best of luck!

Having gone through this multiple times either in new startups or for side projects, here is how I would approach turning your idea into an app. 1. Defining the Minimum Viable Product Your first goal with any new idea should be about proving the idea and finding a market that wants the app you want to build. Achieving that quickly is probably one of the most important thing. To achieve that, you will need to write the specifications that will constitute your MVP. The MVP is basically the simplest expression of your idea to prove it. This step should not cost you much as you can do this on your own. 2. Design the app Before starting any development work, I would suggest you work with a good UX/UI designer to create wireframes and mockups of the app based on the specifications you came up with in step 1. You can find good designers in meetups & hackathons or on website like Dribbble or 99designs. If you want to reduce your costs, you can give shares in the project to the designer. Otherwise, it really depend on the size of the MVP but I would say it will probably cost between $5K-$10K. 3. Develop the app Once you have the specifications and the design of the app, you now need to find a good developer that will build it. Again, you can find good developers in meetups & hackathons or on sites like Github. If you want to reduce your costs, you can give shares in the project to the developer. Otherwise, it really depend on the size of the MVP but I would say it will probably cost between $10K-$25K. For this part however, I would recommend the developer becomes part of the project as his engagement will most likely be higher. 4. Test the app This step is not only about making sure the app is bug free, it's also making sure the app does what was intended in the specifications. To test the app, you can use platforms like BrowserStack or SauceLabs which gives you access to multiple devices/browsers. You can do this step on your own so the cost will be for the subscription to the test platform which would be around $100/month. Hope this helps and good luck with your project.