If you are over 65 and have no other health coverage, you cannot get Part A without paying for Part B. If you decline Part B, you will have to pay for Part A, what amount I have no idea. If you have an Advantage plan, Part D is included. If not you have to buy one. Part D with a $300 deductible, costs $28 and up. With no deuctible it costs $85 and up. If you have Original Medicare you buy a supplemental plan $125 and up per month in order to cover the 20% of medical costs not paid by Medicare.
If you have other health coverage in addition to Medicare and decide to drop Part B, you can enroll in Part B without penalty at any time while you have group health coverage and for eight months after you lose your group health coverage or you (or your spouse) stop working, whichever comes first. This eight-month period is called a Special Enrollment Period.
This information is on the Medicare website. Most of us have limited funds. In addition to the $115 you have to pay for your Medicare plan.
Medicare and You 2012