Hey Makahaman...
You asked about problems and also about maintenance schedules, so I'll give you a bit of input here.
I've had a few hookah compressors and I mostly used them for shallow work, underwater cleaning/scrubbing of boat hulls. They did a good job and I changed the oil on the drive motor every three months. I got my compressor with a Honda 4 cycle engine and it had a "low oil" cutoff on it, which means when the oil got too low, the engine shut off... not good when you're down to 50 feet digging or working. So, you need to check your oil level regularly, change the oil and sparkplug regularly and the motor will run on and on and on...
The compressor end of the package, on small units, are usually oiless, using Teflon coated pistons/cylinders they are good, but they do wear out over time. You'll know when they need replacement, cause they won't be pumping much air. You can buy a rebuild kit for them or just replace the entire compressor unit. I used mine on a daily basis for anywhere from 2 hours to 10 hours a day, depending on my work load. I replaced a compressor once (after nearly 2,000 hours) replaced another one after it took a dump into the river and I have now just replaced my third after nearly 2600 hours on it.
As far as any problems, I've had two. One occurred when I was cleaning a boat bottom at the local commercial fishing pier. I set the hookah unit down, got into my hull scrubbing and after about two hours into the job, I had a rush of water come through the hose into my full face mask and then no air! I came up (was only in 6') and found that the compressor had "walked" off the dock (vibrated off)! So now, I lash my units down to the dock or a cleat to prevent this.
The other problem I had was, again hull scrubbing, I became dizzy, vomitting and could barely get out of the water. Once I got aboard my dive boat, I found that the "snorkel" (breathing air intake mounted on a 3' aluminum extension) had snapped at the base. The bolt at the base of the snorkel mount had actually snapped, and the breathing air intake actually came to rest only a few inches from the Honda motor exhaust muffler!!! This is the honest truth!!!! I damn near died from carbon monoxide poisoning...so, I lash everthing together now. I have my own breathing air intake hard mounted to the wheel house on the boat and I no longer worry about exhaust fumes.
I'm kind of embarrassed to have admitted such a mistake, but I only bring it up in hopes that others may avoid such an accident. I know there are other, professional treasure hunters here on the forum that will have advice for you as well. The only other thing I can say is buy the best equipment you can afford... don't skimp on your breathing gear.
Stay safe, dive safe... and come back to show us what you found,
Wayne
Wayne