You'll get differing amounts and qualities of leads depending on the type of marketing, but also depending on who you're marketing to and where.

The mailers I receive for my properties are not of a high enough quality, to make me believe the sender understands what gets a recipient to even open or read the mailer, let alone respond. 

https://www.biggerpockets.com/forums/12/topics/1122318-quality-turnkey-companies?

They told me that they've rarely had a screen crap out, but if it does, they told me that I could buy a new one from them if I wanted, but could likely get a better deal from Costco and easily pop it in.

Forget the course and put that money on a quality vacation short-term rental.  

Cost per lead (CPL) is crucial—it shows how much you're paying to get a potential seller or buyer’s info, and you want this as low as possible without sacrificing quality.

And for an OOS, I always advise to keep things simple at start, don't get greedy, go for quality and consistency, then work on maximizing monetization later. 

Here's a detailed guide on how to screen applicants: Application Screening Guide 

I know this is an unpopular opinion around here that you won’t see on the front page of the daily BiggerPockets newsletter, but it’s the truth For the record, I still believe a quality STR purchase offers a great ROI over the long term.  

Don't invest in a market if you can't find a quality PM!