1. If this is part time, be very specific about what time you are willing to / can work. This is in addition to the number of hours per week (do you need finals week off, spring break week off, etc.)

2. Consider if this is a long-term commitment you are making or a short-term commitment. For short-term, you probably want project by project billiing–that way you can reject projects that do not work with your schedule. Long-term, you probably want to try for a small retainer fee + and hourly rate…the retainer fee puts you “on call,” which is a better long term fit for consultants, but you lose some of the consulting freedom (this is also heavily dependant on the industry / relationship with the firm).

3. Decide up front what you goals are as you go through school–is this work just for extra cash? Does this work interest you long-term, fit into your future teaching / studies? The more in-sync this is with your future, the more time / commitment you should be willing to make. If this is just for extra money and / or because you like the people you work with, then you should be more protective of your school work and make work a second / third priority.

4. Make sure you come out ahead: As a consultant, a lot of hidden expenses / costs are now on you. The social security tax is one example, increased medical costs, meetings to determine future projects / work is un-paid in most cases, and often you will need to purchase additional software / tools at home as well (these are tax deductable–but you should probably negotiate the firm buying these tools for you as part of your consulting deal).

In theory, consultants should charge 30-40% above salaried employees at the same level (this is actually about the break even point for a company…at 15% above an equal salaried position the company saves money by not submitting SS and medical payments for you). Always try to view both sides of the negotiation–as a consultant you are worth more per hour than as an employee. This allows you to make more cash and the company to save cash–it is a classic win-win situation. Most companies will try to negotiate up-front with consultants to pay the same as an employee at that level. You need to be prepared for this and have the confidence to ask for more AND to show the company how paying you more still saves them money.

All in all, when you already have an established relationship at a firm, a skill that they like, and the time to do consulting for them–these relationships tend to work extremely well. This type of situation is very different from “full-time” consultants who are always trying to find new companies / clients, and usually do not have the same working relationship that you do.

And, yes, if you’re asked to revise something (particularly as I am, which is to say, repeatedly), you don’t want to charge by the job (though some clients insist on it).