I did not test this but this should work.
prontera.gat,150,150,1 script MvP Summoner 666,{
mes "[MvP Summoner]";
mes "What do you want?";
next;
mes "[MvP Summoner]";
mes "Have you come here to summon a^FF3300 MvP^000000?";
next;
menu "Yeah, Sure.",-,"No",M_EXIT;
mes "[MvP Summoner]";
mes "This will cost you 1.000.000.000 zeny. Are you sure?";
next;
menu "Sure.",M_SUMMON,"Nah.",-;
M_SUMMON:
if(TimeSpawned > gettimetick(2)) {
mes "[MvP Summoner]";
mes "I am sorry, but I am not a robot.";
mes "Please wait 30 minutes after your last MvP spawn.";
close;
}
if (Zeny < 1000000000) goto L_NOZENY;
set Zeny, Zeny - 1000000000;
monster "this",-1,-1,"--ja--",-3,1,"";
set TimeSpawned, gettimetick(2) + 1800;
dispbottom "MvP Summoner: Please give me at least a day to recover.";
close;
L_NOZENY:
mes "[MvP Summoner]";
mes "You do not have enough zeny to spawn a MvP";
mes "Get more and come back.";
close;
M_EXIT:
mes "[MvP Summoner]";
mes "Then leave me alone... I am waiting for someone who wants my services.";
close;
}