Hi Katie; Oddly enough, I never worried about or even considered clogged drains for the 11 years that I did house calls. I tried to do mostly small and medium dogs, and bathed then in kitchen or laundry room sinks, mostlly. The sinks had little drain things that caught most of the hair. Occassionally I had to use a tub and kneel... luckily I was younger then and it wasn't as much of a challenge as it would be now! >grin<
I used a Clipper Vac so there was little hair, and what was there I could vacuum up with my trusty CV. I used the one that doubles as a HV dryer, (not terribly powerful, but since I was doing cats, small and medium dogs, it was adequate.)
I used the customers towels, and wiped out the sink/tub after each shampoo.
Happy to answer any specific questions. Best wishes on your new venture! Daryl