<div class="card">
  <div class="card-body">
    hover me!
  </div>
  <div class="card-footer">
    i am footer
  </div>
</div>

.card {
  width: 200px;
  border-radius: 15px;
  border: 1px solid #d0d0d0;
  
  .card-body {
    padding: 20px;
  }
  
  .card-footer {
    display: none;
    padding: 20px;
  }
  
  &:hover {
    border-color: green;
    
    .card-footer {
      display: block;
    }
  }
}