If you accept puppies you also accept the fact that you will be reinforcing potty training which means alot of extra work, lots of extra outdoor runs and probably some accidents, even if at home the pup is good, a new environment and routine can set him back on his potty training. To reinforce potty training, you need to be directly supervising this pup and take him outside as soon as he gets into his pre-business rituals like sniffing the floor in a circle and reward him when he does his business outside. I would remove any rug as well. You can use baby gates or puppy pens to help you keep the little pee monster near you so you catch him every time.
However I would not use belly bands while allowing him to roam freely, instead of reinforcing the owner's hard work in potty training, you are letting the puppy pee where ever and when ever he wants, basically undoing all of its owner's hard work and the pee in the band that is on the puppy's skin might irritate his skin . I know as an owner I would not be pleased one bit if you accepted my pup, probably at a higher rate and instead of helping me out with the potty training and doing the extra work the higher rate is for, I would see as you taking the easy way out by allowing my pup to pee in a diaper.
So if you are not equipped with baby gates and such or willing to take on the extra work of a pup, dont take pups.