Such as, how to attract cell companies to build a tower on your land, what are their criteria, then use something like The Land Geek's Strategy for purchasing parcels on the cheap while staying in line with the need of a new tower. 

Commercial allows LLC's, but the terms offered are not nearly as attractive as residential, so I'd recommend staying in the residential lane. 

But there is not a defined market to sell rented single family houses.Actually, the houses sometimes are worth more if they are vacant, because they can attract homeowners who want to live in them.  

Personally, I haven't seen that in the markets I've been in, but maybe that would attract good tenants and maybe you could get more money per month?

Someone we know has a line on an attractive apartment in Paris that is coming up for sale in the building he lives in.

Placing them on MLS would just attract the not so serious buyers.I am curious to know what steps you would take to get in touch with the right investors and/or wholesalers to get these properties sold quickly.

The most attractive regions of the country were on the East and West coasts with almost half of the investments in New York alone while the other half were split between Southern California, Washington state and even a small portion in Chicago.

They don't stay at home, mostly use the place to sleep and they are out visiting the attractions.

Did you use a freelancer (offshore/onshore) or a company?  

I felt it was very important and would attract a lot of families and potential tenants with pets if I added a privacy wood fence around the property and separate the backyard down the middle to provide privacy to each duplex tenant.