You can spin up a contracting dev team in a matter of weeks, or sometimes in a matter of days. Within a week or two they can be familiar with your team's workflows, and pushing stuff to Production.
But, having good Product context takes time. In my experience, it's anywhere from 6 months to a year before a Product professional to be firing on all cylinders, where they can make the right decision without guidance.
That's a problem because developers won't know what to build, or how to build it, without a clear vision of the work and the specifics of how it should work.
Other than having a stellar on-boarding experience for new hires, there's no way to massively accelerate that context.
One caveat to this of course is hiring from within your industry. If someone already knows your industry, your company, and your product, then they can hit the ground running.
Nine times out of ten, though, you won't be so lucky.
If you can, hire Product before you need them, so that when you grow your dev team, they'll have well specced work to do.