You need to make a business case,
I assume in the past you've used builders you've been happy with, I would advise sitting down with one and discussing your ideas and presenting monetary values to get buy in. If the figures work they might be interested.
There are builders out there that don't like dealing with the business side of things, so if you can take that away from them and save them having to hunt for work as you would be doing that, it could turn out quite fruitful.
I assume in the past you've used builders you've been happy with, I would advise sitting down with one and discussing your ideas and presenting monetary values to get buy in. If the figures work they might be interested.
There are builders out there that don't like dealing with the business side of things, so if you can take that away from them and save them having to hunt for work as you would be doing that, it could turn out quite fruitful.