Seems much more interesting given the type/quantity of responses here rather than whether or not your stats are accurate.

Another way is to pull a cost efficient list of absentee owners from listsource.com searching for the quantity of units you're looking for.

Normally price is dependent on quantity. .80/postcard seems high to me. 

Quantity & quality. 

The more time he can dedicate to growing his wealth bucket, the faster it will grow.If he doesn't have much time or knowledge yet, a syndication for non-accredited investors is good way to learn.He could also put that capital down on a 4-plex and househack.Or find a great partner who has the experience and can put his capital to use in harmony with your friend's investing goals The other options you listed seem too risky if he doesn't have much experience.Good luck 

If you're buying quantity at HD/Lowes, talk to the contractor customer service people and they can discount it for you.

First thing is quantity, postcards tend to be a better option if you are mailing to higher quantities.

Quality over quantity.  

Schools and medical buildings are always good signs of high quantity of people looking for places to live. 

One that doesn’t make money on volume/quantity of piers installed, but on providing professional, honest, and accurate assessments.