One piece at a time. Setting up the right mix of relevant data and red herings is an art form. Especially since you won't be able to get answers to all those questions through a simple search check.
But let's see:
- Who else is interested in the sale?
No-one you can find online - which doesn't mean anything. Tom could have told any number of people directly without using his commlink. But since you are in the round with his close friend, it's likely you get your chance before the other potential renters.
- Has there been any communication between them and the vendor?
That question should be answered by your hack (unless you mean someone else with vendor. I am speaking of Tom Masterson, the landlord)
- Has there been any communication between Mr. Schmitt and the vendor?
None that you could find. And Schmitt certainly doesn't want any direct connection between himself and the boat house. That's why he hired you after all.
- How is the decision going to be made? Is there anything known about the process?
or the criteria?
None that you can find. But you can guess that it's going to be the usual: Stable financial situation, good conduct with the property and its upkeep, sympathetic first impression with Tom and his wife, implying to be a good connection for their interests and jobs.
- Who else has got a say in the decision? Can the family veto? Or his wife?
They both have to agree on a renter. The family would have to prevent you from signing the lease - which they only could if they were present. Once that is done they'd have to go to court to get you out - which isn't likely to be successful from their perspective.