I would ask your CPA at what level he/she thinks S Corps make sense. 

She quickly went to find someone else to talk to.Lots of folks renting out STRs these days are upset by the level of recent competition in the marketplace.

If there's a child who lives in the unit who has an elevated blood level, even if it came from outside the unit, and you don't have the certificates, you're going to be target #1 and you won't be covered by insurance without the certificates.So just on that issue alone, yes, even if you have to put it on credit cards, I would get those new windows in, on all the units you're renting out.

I’ve done some surface level research and know that you can pay third-party services, but wondering if I can outright cancel due to medical reasons for my dad (cancer) who is too weak to travel.

I have a very good grasp of the real estate industry on a macro level and a fairly good grasp within a variety of sub topics within real estate.

Do you have any thoughts on what type of deals fit your skills and interests best?

The decision to fix and sell or rent out your current primary residence is a comfort level choice.  

Most great brokers that will provide top level leadership and a stream of business wont take on part time agents.

It's also illegal to sell goods below cost in an attempt to create a monopoly (drive the competition out of business and then raise prices to high levels).

Those are the skills that will serve you well when you scale to bigger properties.