@lenapesadie has a valid question --certainly a $500 reduced board might make the hassle and risk worth lending a trailer. $6000 a year in board credit would repair a lot of damage and likely pay for insurance.
However -unless the compensation is that substantial, I fall on the “NO DON’T DO IT,” side of the argument.
When I was a kid, I had a scrawny backyard horse (Flicka crossed with The Black Stallion to my eye). Of course there was no trailer, truck, or anything else to get my horse from home to wherever except by riding her there. I swore to myself (as I watched the neighbors’ kid pass in her oh, so lovely, horse van) that if I ever had a trailer, I would give a ride to ANYONE who asked for it --and loan my trailer to ANYONE who needed it.
That lasted about 10 years of adult horse owning. There were too many times of horses who were supposed to load, not doing so making ME late. There were kids whose parents wanted child to ride with me an the horse to the show, then showed up late “to watch” after I helped child unload and tack. One family asked me to haul home their horse and turn it out so they could enjoy the horse show venue a second day. And I was blamed for any every horse that injured itself in the trailer. The LAST STRAW was a “friend” of 30+ years who 1) broke a light off my trailer, then wanted me to have it fixed and send her the bill (that put me in the waiting room of the trailer repair waiting for the fix after taking a 1/2 day to hook, haul, and unhook), THEN the next time she said "Let’s go trail ride (she had no trailer), I said, “Only if you’ll come wash out the trailer with me when we’re done.” (She preferred that I drop her off on the way home). She said, “Why? You’re going to wash it out anyway.” --OK DONE. Never hauled her again. And ended the friendship --no exactly over that, but it was another straw that broke . . .you get the idea.
There is ONE person I would loan the trailer to, or haul —the woman who hauls my horse and me to everyone of our Mounted Archery Competitions all summer long across the Midwest. But I fully expect to arrange to fix any damage (broke a plastic piece on her awning and immediately had it repaired) and I drive 90 min to clean her LQ and horse area after a weekend. OH, and I provide her a horse to fox hunt all winter long --so it’s a pretty even trade.
So again, based on my experience --unless there’s a substantial reason to loan it, or haul, don’t.