I personally haven't sent postcards, I've had good luck with PPC and Video ads. 

I take a picture of their driver's license.I ask for phone numbers that accept texts and any alternate land or business phone numbers.I ask for the names and birth dates of anyone under 18, and ask if there are any service / emotional support animals, together with their names and breeds.I also ask for personal references, previous landlord contact info (and length of time there), employer contact info (and how long there, together with earnings), as well as the name and contact information for their manager / boss.

It's a lot of work upfront but once the team and systems are established it gets easier and as you get better you can expand to another city. 

I personally would avoid over investing in this unit.

I personally like index fund investing in funds like VOO.  

What if the person staying at your place signed a contract but their 1st payment check bounced.

I personally use a company called swift permits.

The person had something of an accent.

It can come from a personal investor who will negotiate terms, or potentially a piece of the equity.

Aluminum siding is a big turn off for me personally.