Can I plan for future while doing meditation on death? Buddha said about meditation on death : "Even if a person aware about his death can be happen within that day is late. If someone thinks, his death can be happen within current breath is not late". According to that, Can we think about future at all? How can we manage neccessery things without thinking about future ? (I know that, for a  buddhist, there can only be one dream or goal. But what about food, money for living ?)

Why meditation on death is a good karma ?

Isn't it a good karma to meditate on other things ? (thinking about failure of an ongoing project, end of a relationship etc.) (However thinking on death covers all)

Sorry for bad english.

King regards.
Not sure where the quote is from, but the instant death that buddha talks about seems to regard the death of the self. He is talking about anicca and anatta, in other words. 

One can of course plan for the future - or ones livelyhood - for instance, but there is a difference whether one plans with attachment or whether one plans with reminiscence of impermanence.