I suspect the right person with the right software and experience can do this very quickly. 

Buy or inherit and hold all their lives while working the properties for income.I've seen teachers, firemen, software engineers and all sorts of people utilize both strategies successfully.

Talk to everyone in your sphere of influence.  

We advertise online through our PM software (Rentec Direct), which syndicates with several websites.  

@Gaston Barua-You would be better served if you had an experienced individual, hold your hand through the underwriting process of scrutinizing a deal with a careful eye ( and with some good software), as no two deals you encounter will be the same.Books are wonderful, only to a certain extent.  

I've worked closely to real estate my entire professional career, 1st in property management and now in construction software.

Most importantly, don't let emotions get involved since this will influence you to skew your numbers.  

Buy or inherit and hold all their lives while working the properties for income.I've seen teachers, firemen, software engineers and all sorts of people utilize both strategies successfully.

As for the question of turn key versus doing it yourself, that will probably be heavily influenced by market. 

Besides real estate, I own a software development company and am a programmer who once specialized in 3D graphics.