Yes! Companies never hire bookkeepers early enough.
1. They can take care of payroll, gov't remittances, year end payroll forms, all your monthly transactions, budgets, pay bills and really anything relating to ongoing financial or even some admin type tasks. How often depends on how many transactions you have, but the norm is at least monthly, if not weekly. They can come in for an hour or two each week to record transactions, discuss any items with you, etc.
2. The main benefit to hiring a bookkeeper is that it frees you up to concentrate on your business. It shouldn't cost too much to hire a bookkeeper, and they are very efficient, often completing the tasks in half the time. This is their job and they do it day in and day out, so become very good at it. Also, they have multiple clients so can provide assistance with best pricing on items that may be common to their clients; banking, insurance, etc.
3. There are many great bookkeepers out there. Ask other companies who they use, or ask your accountant to recommend someone. Some jurisdictions also have bookkeeper certifications, so you can contact the local association for a list.
You can usually start with a contractor, and as you grow eventually bring someone in house. Meet with at least 3 and ask how they would manage your books and have a relationship with you. It is important for you to still be on top of key items such as cash balances and expenditures vs budget, which they can provide to you regularly. Just find a system that works.
4. Bookkeepers and CPA are not the same. Bookkeepers focus on daily/weekly/monthly tasks, providing information but not any opinions. A CPA has a higher level of expertise, having completed additional certifications. They provide advice and other analysis, including certified year end financial statement preparation, tax returns and dealing with the IRS or CRA.
5. It varies by jurisdiction, take a look at Kijiji or Craigslist to see what the published rates are for your area. Your accountant should also be able to help.