Is it better to wait for a tenant that is more on time with payments and leave the place vacant for now or accept whoever applies? 

One thing I would mention though - doing STR just to save taxes often leaves you operationally unstable or too detached from the management to be successful.

I mention to them that I would be interested in their house if they ever think of selling it.

One mistake could extend the tenant's stay for months without any income, not to mention the stress it could cause.

*Please note: As Dave mentioned, not all REITs allow for ongoing depreciation, but some do.

While no one else mentioned it, I will. 

Quote from @Jake Hughes: Called my CPA and they mentioned that aside from tax write offs we can do a cost segregation study on one of my properties.

Each renter profile comes with its own booking patterns and renewal needs, as you mentioned... but we find that a 30day rental period with option to renew and automated reminders to the renter works great!

You can definitely integrate Zelle/Venmo into your systems but there's easier ways. 100% agree with this explanation BUT I think there is a sweet spot not mentioned. 

The tax return you have should have a 'carry-over' schedule providing details as to what is carried forward to the next year, whether it be an NOL or a capital loss carryforward.As Michael mentioned above, there is no carrybacks at the moment.