1) If you're not married, you don't have any rights to inherit, EXCEPT as he puts in his will. A will can leave property to anyone, regardless of legal or blood ties.2) In the event of his death, property you can prove is either yours or at least partially yours (e.g. you have a receipt showing you paid for it; you have a canceled check showing you reimbursed your boyfriend for 1/2 the price) would go to you, in whole  or in part, though proving your ownership can be very difficult.3) The best way to protect you is by a combination of a will, insurance, and having certain assets owned jointly (a home; a joint bank accout). A lawyer can guide you and your boyfirend in doing this, and also take care of other issues, like powers of attorney, medical treatment guidance, and your right to continue to reside in a home owned by your boyfriend.As to that last point: if the house/home is owned by the boyfriend and you do not inherit it under a will when he passes, whomever does inherit the home could evict you. There are ways around this, such as by giving you a life estate, or the right to reside there--but as the will, insurance, power of attorney, etc., this needs to be planned and worked out in advance.