I know there's a 2nd game out but will the first continue to update and will I have to pay again to buy the update or if I buy once will it be free
There is one more content update to account for Rachel Milf Tournament win. Should be similar to the most recent one with Jessie. There is also a resolution update to bring the in game images to the same standard as Zombie's Retreat 2.
You shouldn't have to pay again. All you would have to do when the update goes live is re download the game. An since you already paid for it, you shouldn't have to pay again.