So, they could potentially buy another house later on.

We all invest in real estate in order to make money, and keep in mind that someone who can only afford to live in a mobile home and seller-finance to buy the land is probably tight on funds. 

You buy today so that you pay less than if you were buying when you retire and hopefully you make some money along the way.

According to NYC, STR is hurting housing affordability just like normal people can buy a house or condo near the Time Square and Madison Garden. 

Nobody ever went broke over a duplex, I know this now,  but I have to admit I had some serious doubts about this when I started 16 years ago, I bought every course I could find, already on CD's, this was post cassette tapes lol, and I paid RichDad Education for a one year coaching program (turned out my coach was a girl in a call center without any actual experience). 

Most fail to consider what goes into owning and operating real estate once it’s purchased and solely concern themselves with how to buy the property.

Not following this - what does your buddies property have anything to do with a property you are buying?  

Would that be, for example, if the PM says, "I manage a duplex for John Smith in Turlock," then I call John as a reference, ask John a few questions, and then ask John the address of his duplex so I can later look it up on the county website and verify if he is the owner?

I was trying to work with them to buy more property in different markets and get it under a Master Lease with them but they have been really picky.

My wife and I also invest in STRs and I spend a lot of time working over the best place to buy our next property.I've been looking at Packwood recently for a client.