You might spend $3000/month or more mailing post cards, and making a ton of phone calls, or just driving for $.Buying from many wholesalers is risky. 

If you just send the standard "will buy your house for cash" postcards, or do generic bandit signs, or canned PPC internet leads, you will waste all of your time on crap "leads" that aren't real.

Postcards and letters.   

Door knocking, postcards, cold calling, etc. are going to be the best bet for finding something that is going to hit the numbers you need. 

You can even send postcard to the list you get directly from the software. 

Or do you wait until a postcard/phone call is returned and you set up a time to see the interior of the home?

I will definitely send Letters, Postcards, Call, and Text, but how often?

Direct mail has been my best source of leads...letters and postcards. 

You can write letters or postcards yourself, type them out, or invest in service like Openlettermarketing.com. 

And while you are making phone calls, sending postcards, or knocking on doors, know that there are many others doing the same.Five years ago I didn't receive a single phone call about any of my properties.