The standard item that family-friendly rentals have is a pack and play. It can be packed down and stored and it’s easy to set-up and breakdown. Sometimes the hosts have it set up for us and sometimes it’s in the closet and we set it up ourselves (takes around 5 min). You don’t need much bedding as babies aren’t supposed to sleep with blankets or anything else in the crib (suffocation risk). There just needs to be a sheet to cover the pad. Basic pack and plays cost around $50 although I’ve bought 2 from craigslist that barely looked used for $15-20 each.
If you are going to have young children in your rental, make sure you have waterproof mattress pads on your beds as little kids often end up sleeping in the bed when traveling.
There have been a few times when a pack and play was a deciding factor in which rental I chose as it’s one less thing that I have to arrange (I rent baby equipment if a rental doesn’t supply it). I’ve stayed in over 10 rentals, most family-friendly, and no one has ever had a high-chair or any other kind of furniture besides a pack and play. A few units had a little bin filled with some toys and books (stuff that belonged to the owner’s kids or grandkids). The toys are always a big extra and totally unexpected and very appreciated as it distracts the kids to see unfamiliar and “new” stuff.