local rates vary immensely! call around to the local doulas and see what they are charging. even a few hours distance can be a big difference. I am 2 hours west of philly and we charge about 1/3! Also, you would probably start on the lower end, but I believe in not being so low as to undersell the other doulas.
I heard someone mention once about looking at what other professionals charge by the hour or service call, like lactation consultants, plumbers, repairman. This gives you a rough estimate of your charges if you multiply that by the average number of hours of work. what are nurses making in your area? around here, they start at 17.00/hour, so i guess if we assume that the average doula around here works for 10 hours (we don't usually go to homes, we meet people at the hospital), 2 prenatal visits (3 hours) and 1 postpartum visit (1 hour) for a total of 14 hours X 17.00=238.00. I add in supplies and gas and come up with about 275.00, which works out around here because the average is 300.00. Other places, I hear charge 1200.00 or more, that's what we charge for homebirth midwives.
i charged a bit more because I am also a nurse, midwife, and lactation consultant and usually did 2 postpartums, one of which was a lactation visit. And people didn't bat an eye at that.
Good luck! Remember that you can always change your fees, you want to be able to work and make money, not spread yourself too thin.