Perhaps you are familiar with Garrett Planning Network (GPN). If not, all Garrett advisors provide hourly-based pricing services. All Garrett advisors are RIAs and CFP (R). They charge based on the amount of time involved to work with and for you, and your advisor will provide a written agreement outlining the services and cost in advance.
Regarding your specific questions, the hourly rate can vary, depending on your location and the individual planner. Costs can range from $150 to $300/hour and up. I would suggest you interview 2-3 hourly planners in your area. They should be willing to tell you their hourly charge up front.
To put in a plug for this business model, which I will fully admit that I have a biased opinion toward. The hourly fee may seem to be a large upfront cost. But when compared to some other models, it is often much less costly in the long run. Much like an CPA or attorney, you pay only for the services you need. It is not uncommon that I will structure a comprehensive plan that can save a client ten to hundreds of $1000 over their lives. That means more money in their pocket to achieve their own goals.
You can find a hourly planner at http://garrettplanningnetwork.com Full disclosure - I am a member of GPN.
Hope this helps.
Andy has some good advice. Planning costs may range from $1.5k to $3.5k depending on the complications with your personal situation. If you are looking for portfolio management some planners may charge a flat fee and others may charge around 1% of your portfolio with this percentage decreasing depending on the size of the portfolio. Here is a decent article you may want to read: http://www.bankrate.com/finance/savings/financial-planners-not-just-for-millionaires-anymore-1.aspx
Andy and Glen provide some good points and I just want to elaborate on Glen's statement that planning costs range from $1,500 to $3,500 generally. Often you'll find that an advisor may say their hourly rate is $200 but price the planning they'll do for you on a flat rate. For example, I may tell a client my hourly rate is $200 and their plan will cost $2,000 because I would expect my work for them to take approximately 10 hours. I would say in many if not most cases, when the planning is done and you divide the flat fee by the # of hours spent, the hourly rate for that case is much less than the $200 (meaning the planner spent much more than 10 hours). My point is don't always just compare hourly rates but the total cost of the planning. ...and remember, you usually get what you pay for.
KC the 3(16) service is for a 401k or 403b plan correct?
Fees for a 3(16) are all over the map because the services aren't all the same. Some retirement plan providers will take care of a number of the responsibilities that fall under 3(16). It's only recently that we've come across vendors saying they'll be the named 3(16) and the prices have varied tremendously. I'd echo all of James Holland's comments regarding extreme due diligence and add this: if you're hiring someone who doesn't work for your company to oversee the 401k, they better intimately understand your company and employees so they can act in their best interest and be someone that you'd trust with your own mother's bank account too.
Hourly fees should be in the range of $150 - $300 per hour. Fees that run to the higher end of that spectrum usually involve some complex estate planning or non qualified retirement planning for business owners.