Get pre-approved for financing, then look for deals on Zillow, through direct mail, or networking.

Using a lower-cost skip tracing service and then a call/mail/sms campaign service separately may reduce your costs.

If you only want to mail, you are all set.

At the time I was running on direct mail.

Quote from @Jonathan Greene: I like DealMachine because they have skiptracing including in Pro now, but I still think of it more for neighborhood canvassing and mailing (aka driving for dollars) than multifamily acquisition opportunities.

I am thinking in running a mail campaign to hit some deals off market.

Perhaps combine a direct mail campaign with your text message and cold call campaign.

I’m relatively new to wholesaling, and I’ve been diving into the process—cold calling, direct mail, and driving for dollars.

We allow Tenant Portal (ACH), Direct Deposit to our bank, Venmo, Strip (credit & debit cards) and old-fashioned mailing of checks. 

I don't get the non-refundable deposits, people often call that a junk fee.