realloc question

char *message;
char * one = "hello";
message = realloc(message, (strlen(one)  +1) * sizeof(char));
strcpy(message, one);
char *two = "test";
//add the size of the second string to the size of the message 
message = realloc(message, (    (strlen(message) +1) + (strlen(two) +1)     ) * sizeof(char);
//add string two into message
strcat(message, two);