I used to just lay our bikes in the bed of my truck when we wanted to take them anywhere to ride. Not good. Pedals got tangled in spokes, paint chipped where bike met truck, and I was flirting with real damage.
I’m too cheap to buy a Thule rack, so I dug up some bolt-down “bike blocks” on eBay for $11 apiece, and figured out a way to make my own rack with two 2x4s. I found those in a friend’s waste pile, and I already had the screws and bolts I needed, so my grand total investment was $33!
What’s more, I figured out the dirt-simplest way to make the rack.
I was nervous that the handlebars would bump each other, but my bike is more serious than my wife and daughter’s bikes so my handlebars are set lower then theirs and don’t bump at all.
If you put a road bike in the middle and two hybrids or mountain bikes on the sides, I think that would also work, and if all else fails, you could just cock the bike mounting blocks slightly when you bolt them down, which would twist each fork a little and offset the handlebars.
If you are carrying three bikes, you have to climb up on the truck bed to attach the middle one to its block, but the side bikes are easy to put in and lock down. I even found the perfect bungee to hold the front tires in place. Score one for the cheapos!