Bike racks are like photo tripods. If you cheap out and get something to save money, you’ll end up buying several racks, go through a great deal of hassle, and in the end you will have spent more (in addition to potentially having bikes damaged) than you would have spent on a great rack that fits your needs perfectly and lasts forever.
A really GREAT rack, that does exactly what you need and is of great quality, is almost a one-time purchase: barring surprises or big changes in your life, you can have it for decades. Buy well once, and you’ll live much more happily ever after.