Wow... a lot could go wrong here.
Have they had large dogs before?
How old is the pitty? Have they had him scanned for a chip? Any vet should be able to do that.
Is there an animal shelter in the area to notify that they've found this dog in case the owner is looking for him?
While they may want to keep him, is it best for the dog if they do? With both working and being gone all day, it will not be easy to train him properly. If he can't be kept safe, protect the house and the other pets till he is, it might be best to take him to a shelter or find a rescue for him.
If they're going to try to keep him, he should be neutered ASAP. Crate training him is very important as well and may not be easy to do. Tying him would be the absolute last resort. Purchasing a an outdoor kennel to keep him in, is slightly better.
Bully breeds can be wonderful dogs but are not for everyone. They are very strong dogs and need a lot of attention & exercise. Some have high prey drives which make them not good with smaller dogs & cats. Do not trust this dog with the resident pets just yet.
Have them check to see if their insurance company has a banned breed list. Pits have a bad reputation as you probably know and are not favorites of insurance companies.