@Steven - More feedback from one non-technical founder to another vs. a direct answer to your question. The problem I had with taking your same approach (I paid to develop my MVP vs. an incubator/angel funding), is that after it's built you're left with needing numerous iterations until you get the product-market fit right -- and each iteration has a price tag associated with it. The simple fact is 99.99999% of new products need numerous iterations after the initial MVP. And that's true even with established companies who are significantly supporting the project with money, developers, product managers, and customer researchers.
If you strongly believe that you need a more functional MVP, than I'd agree with @David that you really want a co-founder by your side who is willing to stay up late knocking out a new build so your early adopters will see the changes they need, shortly after you meet with them and understand the issues of your current build. That person would not just take direction from you, but would have their energies invested in developing a product that delivers what is needed both for your customers and for the long-term growth of your business. A development firm will always be happy to take your money, but I'd suggest their biggest motivator is their bottom-line and not your long-term success.
Yes, it takes longer to find that person. And it is tempting to just jump in and go. But in the long run, I believe you will have a significantly better product since you took the time to find the right person to collaborate with, who is just as passionate about the project as you are.