How much should I charge?

Here is an excerpt:

By now you've probably gotten the idea that grant writing is a lot of work, so even if you don't have a proven track record you need to charge enough to make it worth your while. You can charge by the hour but I wouldn't charge less than $50/hour even if you've never worked on a grant. That is rock bottom and if you've got a track record as a freelancer that's not much money. Some grant writers charge by the project, say 10% of the value of the grant. A grant that will bring in $1 million per year calls for correspondingly more work. If you're trying to establish yourself, you can work in a bonus if the proposal is funded, but either way, you get paid. If a client wants you to do most of the work in a short period of time (say, one month) charge them accordingly, or I promise you, it won't be worth your while.