This service works with most mobile phones with interest access, so the provider's monthly charge should apply, however, the receiving party may be charged according their carrier's rate. Contact your provider for specific charges.
TMobile Prepaid Phones do not provide a monthly charge. Instead, you purchase your minutes upfront which do not expire. These minutes can be used as needed. If you tend to use your minutes quickly...
Each ISP has different charges for different access speeds. There are websites like wirlpool.com that will give you a comparison of speeds and charges.