interval between getting passports done and appearing for the visa interview

[dibbu]

hi,

i would like to sponsor my parents visitors visa (tourist,B2)...they are going to get their passports in a week....i am thinking to send them for the visa interview as soon as they get their passports....should there be any gap between getting the passports done and appearing for the interview???
i would appreciate ur help if u can answer my question...
thanks a lot

[immihelp]

There is no law for any gap. They could go the next day if they wanted.