Each of these properties is in a different location and was purchased at a different time.

Are you interested in a specific startegy (brrrrs, flips, vacation rentals, etc)?

If rates come down at all I predict we’ll be back in a strong sellers market (competitive offers, steep appreciation etc) because inventory is still low. 

I keep a mortgage on each property and own them in a couple of LLCs. 

However, a lot of concerns can be mitigated with looking at their past rental behavior in a lot of different settings.

If that co-signer isn't in a position where you can force them to pay if things go sideways, then the fact that they co-signed is just a promise and you can't cash a promise!

It allows you to live in a home that meets your needs while offsetting mortgage expenses.

I've seen the Speed Queen SF series recommended in a few places.

Understanding STR regulations in a market is an essential "must do" when it comes to evaluating a short term rental.

Perhaps....but   the person relocating to any given market and who has to make a purchase in a finite period of time is generally the least likely candidate to get a great deal on the purchase, meaning the appreciation is even more important.