What you have read here is correct and should be followed if possible. I was in your position a few years ago and remember similar issues. I did begin to work regular with a few bands and got to know them well. We negotiated a compromise deal that has proven to be OK in my situation and might work for yours.
I was carrying a heavy rig at the time (more than this geezer could move alone) and had to pay help every night from my fee. Helpers wanted pay even if the gig was cancelled, exactly like we want. The deal with the bands that I decided to stay with went like this:
I will lay off my helper. A minimum of one and generally two of the band will arrive when I do on my schedule and assist with all load in, lifting, placement, and will learn to follow my instructions and assemble the rig with me, to include lighting. At the end of the night, a minimum of one and generally two will stay until my trailer door is closed and will learn to carefully dismantle and pack the gear. They learned to roll cords my way, and where every item was packed.
My load in/out time was cut in half (that was 2-3 hours per show.) They learned a respect for what I do and provide, and why I charge the rates I do (which are cheaper than many here, but more than bands like.) I made more money per show because expenses dropped and I invested less time. At the end of the year, the cancellations were offset by the extra revenue when shows went as planned.
Then I picked the band that worked the best with me, did the most help, and paid the most, and most importantly had the best chance of long term success.) I told them my company would give them an exclusive service contract if they kept me busy, held up their end of our deal, and kept politics, grief, and misery to a minimum.
By the end of the first year with them, the band had improved and the rates for the band went up a LOT (we started doing playing for more than twice what we were getting before.) The band just started raising my pay because they realized the effort I put in and because they could afford it (I get from 25% to 200% more each night now.) They also attributed much of their success to my PA/lights and didn't want to lose their advantage. If someone threw a tip on the floor, they also gave it to me ($100 bill more than once extra at the end of the night...)
Make them share the work when times are good so that when they are bad, you won't hurt as much from it. Sorry this was so long, but maybe you can come up with a "deal" with the bands that are the most reliable and seem to have the most future (read that as best chance of paying off on your investment.)
Good luck and I hope you can sort this out. If you can take the legal contract route with deposits, you have to be inventive.