Can anyone make some suggestions on some reasonably priced companies that print and mail yellow post cards? 

I have found that Yellow Letters/Post Cards are a great lead source.

I bought a list from ListSource and sent out postcards to a few hundred absentee landlords in the area where I want to invest.

I'm looking at using a scratch-off style of postcard with an incentive to get the homeowner to bite at the call to action.

Yellow letters are popular, any form of mailing with the exception of postcards in this instance.

Sure, some people have sent a few hundred letters or postcards here or there...but is that who you want advice from? 

I started with driving for dollars looking for a property that looked distressed in my farming area talked to the neighbors and looked up the owner over the driving for dollar app and mailed the owner's a postcard/letter Good luck!

Take down the addresses of tired plexes and send those landlords a postcard. 

Find an area and type you like and send letters or post cards to the owners themselves.

Mailing is easy, and you are leaving people with a postcard or letter they can keep (I have had people call me 9 months after they received a postcard), but it can get expensive.