What's their motivation, and why are they selling?

A lot of companies will send you pre-sorted first class, but if your pure motive is saving money, don't use that route. 

They are motivated to sell but there is a slight problem.

I am a mature and motivated 19 year old student who is on a mission to help my father gain FI after he has worked hard for 42 years.

I have a full time job so it is hard for me to focus a lot of my time on motivated sellers with mailers or drive for dollars. 

I've been putting up bandit signs all over Orange County, searching through Craigslist and sending out direct mail, but my phone hasn't started ringing yet with motivated leads. 

Structuring the partnership is key , it should be motivating enough for the person on ground to take care of property like their own.

These sellers don't seem as motivated as yours were.  

I am eager and motivated.

It's equivalent to your car breaking down and needing to being in the shop for a day and costing a few hundred bucks, happens all the time.Towing a car hurts of course, hopefully enough to cause a tenant to pay the rent the promised to pay, but it's not a death sentence, it's not kidnapping children and pets, it's just another fee and hassle to the tenant to motivate them to pay.