They are there on time reliably, do a good job managing inventory/off site laundry, and generally do a good job cleaning overall.

Not a book, but Bill Faeth has a lot of free, good content on his site and YouTube videos.

The risk is too high of losing everything.

There was a recent webinar, bottom line, it looks like Darryl Heller sold off many of the ATMs, didn't pay the people who put the cash in them, didn't pay the stores that have them on site, isn't providing information to David Zook's team that the court has ordered and is racking up something like $50k+ a day for not doing so...it is a complete mess and seems like there are only a fraction of the ATMs that might still be producing money but the company hired by Zook to get their hands around all of this is running into many roadblocks because Heller's team isn't providing info. 

Whether it’s Christmas morning or a regular weekday, acting quickly can be the difference between closing a deal and losing it to someone else.The holidays often feel like a time to slow down and relax, but in real estate, urgency wins.

Have you ever heard of a Landlord being sued by a Tenant and losing property?

Once you are on site you can decide if your $20K should be used as a downpayment on a double to house hack (to stop renting), a single to just stop renting, or a single to lease out.

This is a real estate investment forum, so you won’t find many/any people on this site who deploy that strategy.

Their customer support is terrible and some of their software, but they have about 8x the site traffic in general than Airbnb and VRBO combined, surprisingly.  

I am aware of Crexi, Bizbuysell, and Loopnet and reach out when I see something for sale on those sites.