Your questions raises a number of issues. Let's start with the focus of your question and then raise and address what appear to be other significant issues that might be involved. Since you are raising the question about terminal illness, we assume you are concerned with medical costs, nursing home costs, etc. The first thing you should do is meet with your insurance consultant and review your health insurance coverage and determine what is covered, what is not covered, and what you can do to plan) to increase the likelihood of coverage, etc. You probably, in light of your situation, should meet a financial planner to project how your income and assets can be used to cover anticipated expenses. Finally, and perhaps this is the heart of what you were asking, you need to meet with an elder law specialist (this is not a general estate planner, elder law is a sub-speciality with different expertise) to review whether or not any asset transfers an be made that might safeguard some of your assets from being used to pay for your care, thus preserving them for family members. When you meet wit the elder law specialist, be sure to discuss the recent law changes that provide for a five year look-back period (the period during which assets transferred can still be reached to pay for nursing home and other costs). Given that you have a terminal illness and the long duration of the look back, be sure you understand how any asset transfers might be effective. If they clearly won't be, according to the elder law attorney you consult, it might be counterproductive to pursue that planning. But before you throw the towel in, read on below as there might be some other avenues that your planning team (and yes, you need input from a number of specialists) might be able to guide you with.

You really need to sit with an estate planner (in this case the attorney helping you with elder law issues may be able to guide you), and a financial planner and review the title (ownership) of the assets you have. It really, sorry to say, sounds like a mess. You have assets owned jointly with several different people. Depending on those "joint" ownerships are structured, on your death your sister, mother and husband might all receive immediate ownership of different assets. Depending on the details of joint ownership (see other Q&As and planning articles on this website for more information on title and ownership) your will may have no impact on who receives these assets or how. If you really intend your husband to be your primary heir, he may not receive many of your assets (e.g. assets owned jointly with other family members may pass directly to them). You also need to be carefully because the federal estate tax laws (you mentioned nothing about estate taxes!) presume that the first to die of a joint owner owned for estate tax purposes 100% of the assets, and in the case of a spouse 50%. Thus, if you are holding money jointly with your mother that is her money, and you have a terminal illness, unless your mother can prove she contributed to those assets, they will all be taxed in your estate if you predecease her. A mess (sorry!). But in this mess may be a possible planning idea. Who really owns the joint assets? It might be possible, and make sure you get really good help from an experienced elder law attorney, that some of the joint assets can be demonstrated to be other family members assets and not yours. This might provide a mechanism to change title and not trigger the 5 year look back. This might be a very gray area of the law so proceed carefully and only with expert (not general) professional guidance. But within this idea might be a kernel of planning to provide significant benefit to you and your family.

Finally, (well not really, as there are so many more issues raised by your question), consider some of the following: be sure your power of attorney, living will and health care proxy are up to date. If you live in an estate that has an estate tax, review planning to address that. Take time, however, hard, and get your personal affairs in order.