It sounds like you've already got some solid experience under your belt.

I would not overthink this, but would start by building a solid professional relationship with your tenants.

I'm having trouble finding any real solid information, experts, or sources on the subject, so I figured I would reach out to the BP community. 

Selling now avoids capital gains tax and lets you reinvest into a new primary home and a solid rental property, which feels like the safer play given the cash flow challenges and ARM timeline.

I'd make sure the rental market is solid before buying a property.

Make sure to have a solid plan for the rehab and your exit strategy to make the deal more appealing!

Building a portfolio with your brother-in-law sounds like a great partnership, and Cedar Rapids is a solid market to start in.

Ideally, I’m looking for areas with a mix of:High occupancy rates for STRs (Airbnb or VRBO),Solid potential for appreciation over the long term,Investor-friendly regulations on short-term rentals.If anyone has experience with markets that fit these criteria or knows areas where STR is thriving with good investor laws, I’d love to hear your thoughts.

In my Carolina Beach market you get solid 2/2s for 575,000 that gross $55,000 for example with pretty low HOA fees annually 7000. 

They’re a great way to learn the entire process of property investment, from acquisition to management, and provide a solid foundation for scaling your portfolio down the line.