You need a lot of money to buy a radio station, since all the frequencies and the licenses that go with them are taken already(the "non-profit"" frequencies are generally assigned to educational institutions, and have all been taken, as well)--There is a movement to allow some new low frequency community stations (there have been a number of illegal "guerilla" low frequency stations that have popped up lately)--
Of course, you could set up your own internet radio station, but the ASCAP/BMI licensing fees are really expensive for them--Next best bet is to find a low frequency station and volunteer to do a show--

Probably the best person to talk to around here is our resident seasoned radio pro, Ron Olesko who not only does a wonderful on WFMU-FM, but has been very supportive of all things related to folk music--