Additionally, the HOA me to file an insurance claim due to $20k+ worth of water damage to my unit, which I did, but now I’m unsure if I should have filed it or if the HOA should have.

Things to look for are low rents, kitchen remodel, addition of a bathroom/bedroom, amenities that tenants want.

This apartment is not producing any cash flow; rather I am paying additional $400-$500(including HOA and mortgage payment) from my pocket every month for last one year.

I am not sure what you will create will be able to add additional value?

Quote from @Renee White:@Renee White one thing I would add in addition to @Jackson Surplus's great tip, is that Wisconsin like Iowa, has the amazing benefit of snow (kidding, kinda) lol. 

To take it a step further, you really want to be named as an additional insured.

I know this is a lot but additionally, I am curious to know how the number of beds/baths affects the overall result in terms of cash flow for both single family and multifamily.

Good info, but this is not new info, if you search on here there are a plethora of posts.In addition to being an STR investor personally I am a PM with 60 or so doors and also do acquisitions for clients. 

They never talk about permitting.For example, Henry often talks about converting a sunroom by adding insulation, heating, and cooling to add additional square footage. 

It actually is illegal to take on additional debt during a Chapt 13.