When I check the county site it shows the the same address I have on my postcards

I am going to send out 100 yellow postcards to vacant free and clear houses in Philly.  

First batch with postcards using first-class, then follow-up with yellow-letters using standard mail.

I purchased a list from List Source which I was initially excited about and really enthused to get my postcards out the door!  

After an exhaustive search, I've got a set of high converting postcards and we're going to do 6 touches for each name on the list.  

Sent out 2750 pieces (mix of yellow letters/postcards) to absentee owners and had about 40 calls come thru.

Start throwing signs, going to 2x meet ups per week, postcards, letters, craigslist, bush buys etc.Go to home-depot when they first open in the morning all the great contractors will be getting ready for the day.

Can someone recommend a company that offers affordable postcards with shipping included?

A few days prior to the open house, take an open house postcard and walk 6-8 houses on either side of the house, and the 12 houses across the street. 

Also where did you get your post cards, how much did you pay for them and what did they cost to ship?