separation agreement

hi, i'm from pa and i have separated from a 22 year relationship (never married). he is staying in the jointly owned home and we have agreed on a cash settlement of the property with my portion being paid upon his death. i do not have a lawyer but his has drawn up papers for us with the recommendation that i have them reviewed by a lawyer. his lawyer said that by placing a first mortgage on the property i will indeed be paid my previously agreed upon amount immediately upon his death. my question is this...is that the best way to go? what if he marries or someone else moves in with him, will i have to fight for my money if that person doesn't have the cash to give me at that point? i don't want to have to be going through a hassle to get what is rightfully mine per our agreement. there is also the option for him to pay me cash anytime prior to his death should he so decide to do this. all other material things have been settled and distributed except this issue. thanks so much for your assistance with this issue. i would appreciate an answer as soon as possible before i am required to sign the forms.