or just do both from the same account?

Google frowns on two accounts, so unless you know how to fly under their radar, use one for both.

Ok but say if i had a dead site this wouldnt effect my income on an active one?

Not if we're talking about AdSense, no.

technically you should only have one adsense account per person/business.... but if you have multiple business you are ok.

And bingo was his name-o

you can not do that.google will k u if you did.

If you have multiple businesses as stated above then you can do this. If you are trying to make multiple accounts using the same data for signup then google will disable either one or both of your accounts for this. Just run them both under the same account, you'll not be negatively effected by doing this.