It depends on what you are manufacturing to how difficult its going to be. You don't say. Manufacturing can be a highly leveraged capital intense business. You will need steady revenue to offset such expense.
Case in point, I have two colleagues that manufacturer for different clients. One is a machine shop that serves the Semiconductor industry. This is small specialized products that apply to older semi technology, but are very lucrative in revenue as competing with the OEM's is easier.
The other is a machine shop that deals with high end, fortune 500 companies such as GE and Rolls Royce. Contracts for this person came from his time at GE, and they were willing to have him supply as he was supplying capacity, cycle time and cost, his value added or competitive advantage. Two very different markets, but both highly leveraged.
What are you offering your industry clients that they don't already have from their existing suppliers? Whats your added value? Whats your competition? These are some of the basics you will have to overcome, apart from the startup costs.