It depends on if you are getting fair market rent, or giving them a sweet deal.

Buy them in the sweet spot for mileage used (50-75k is a good target), drive them up to about 150k and then sell them before they're worthless;3.

@Ian Walsh Simple, sweet, and to the point.

Every market has a “sweet spot.”

I cook all dinners and most all breakfasts.. this morning a few eggs and sweet potato pancakes.no one I mean NO one is allowed to touch my cast iron skillets.. they are seasoned to perfection.. and then I use my green egg at least 5 nights a week for whatever protein I am going to cook.. plus I do the dishes.. 

Trying to find that sweet spot of close enough to drive, but far enough to not have the deal with the NY metro area nonsense

Unfortunately, my previous Slimelord property management employer would take their sweet time processing the applications to get more application revenue, because they're such a poorly run business, and they're Slimelords, that I would have to keep going out there over and over, and it would skew the rental figures. 

I was set to make a sweet 30% return on my cash.

In my city, prices are up, so the buy and holds are not 'quite' as sweet as 18 months ago.

Sweet, I can't wait till I get my first one.