But actually I do have the money to pay for this stuff. I've lived here for almost 30 years and I know things are going bad.

So you call it an "Interior upgrade"? Maybe it's better to think of it as that. Because truthfully there are other things that need doing here also.

This is not uncommon in the winter in Colorado where they come in out of the cold and leave as soon as it warms up (Rattlesnakes are very unlikely to enter houses in the winter but hibernate earlier). That's what my "guy" did and I have seen no evidence of rodents for some time. When it warmed up, I had a home inspector come seal any identified ways for rodents (or snakes) to get in and so that will probably be a one time thing.

But, while my basement is partially finished, I really only go down to do laundry so I was happy to honor the cohabitation relationship for a while. Better a bullsnake than rodents, including those that can carry Hantavirus out here.

made sense. Those rats can do some damage. I've watched a turn of the 20th century murder mystery show called, "Murdoch Mysteries" where one episode had dogs put in a boxing ring type thing and go after the rats that they put in their also. People would bet on how many they thought would be killed, (something like that)

Found many mice and roaches in kitchen appliances. In furnaces, I found many birds, a few bats, a couple snakes, and one squirrel. Some of those cases I will never forget.

Just curious because the "professionals" here today both freaked out because of the rats.

Not really freaked out. Just memorable for being out of the ordinary. The squirrel was very sad, it was young, and had gotten down the vent pipe and died at the furnace draft blower. Same with all the birds and bats. The kitchen vermin, I was required by my company to cease work if I saw roaches or mice, and calmly tell the customer that I cannot continue until after they show proof of an exterminator visit. Some times you don't see anything until you remove a panel, and then a flood of hundreds of roaches tumble out. Still, I never freaked out, that would not be professional.

(You can't have too many cats, imo)