How do you do rapid prototyping?

I’ve been getting into government contracting for a while and finally landed one, so I started building out the solution. The issue I’m running into is that the requirements keep changing while I’m already in development, but the deadlines don’t really move with them.

Right now it’s basically just me doing everything end-to-end, sometimes with one other person helping. So I’m handling the prototyping, building, and eventually I’ll be responsible for deploying and maintaining it too.

The biggest problem is the prototyping phase. By the time I build something that matches the current requirements, they’ve already shifted, and I end up reworking large parts of the system. It’s starting to slow everything down, especially with timelines that don’t feel realistic for the amount of change happening.

How do you usually deal with this kind of situation?

Specifically:

- How do you prototype when requirements aren’t stable?

- How do you prevent constant rework?

- Is there a way to structure the system so it can handle changes without breaking everything?

Just trying to figure out a better way to operate in this kind of environment, especially with a very small team of one.

My goal is to establish a system for smaller projects. The project is not that big. Its more of an add on to a much larger piece of software. I hope and pray to acquire more of such work and eventually make enough to pay my bills lol. But i need to establish a system first. Any advice is helpful thank you.