1. Get a virtual mailbox, then file the certificate of incorporation through a cheap service.
2. Get a lawyer to put their address as incorporator.
Virtual mailbox is a continual cost, lawyer is one-time. Is that the major distinction? If I plan to be in business three years, then the lawyer already pays off, no?
If you plan to make a one-man SASS product you might be able to get by without one, and maybe the mailbox makes sense. But if you plan to build a real company (with employees, terms of service, contracts, legal counsel to avoid getting sued, etc.) you're going to need a healthy relationship with a lawyer anyway, so why not start one now?