You can do it in one function, you just have to check for each post type. Rather than returning
if ($post_type == 'car') {
// do the car post type
}
if ($post_type == 'house') {
// do the house post type
}
If you used the same field name for the acf field on both of these post types then you could do something like
if ($post_type == 'car' || $post_type == 'house') {
// do the house and car stuff
}